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The Cape Arc of Meridian

Date de soumission : 08/07/2009
Critères: (ii)(iv)(vi)
Catégorie : Culturel
Soumis par :
department of Cultural Affaires and Sport, Provincial Government of the Western Cape
Etat, province ou région :
Western Cape Province, Republic of South Africa
Ref.: 5461

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Since ancient times, Africans and people all over the world have wondered about the shaped of the earth. At the same time they looked up at the night sky and contemplated the stars. Stars like lsiLimela (known to Europeans as the Seven Sisters) and the Giraffes (the Cross and the Pointers) indicated the time to dig and hunt and plant. The Swazis kept a very-accurate calendar by the sun. Legends grew up around the sky as well, telling how a young girl threw ashes from a fire into a sky to make the Milky Way, or how the Sun was made to give light to the earth when people threw him into the sky.
The sites, beacons, terminals and structures related to the Geodetic Arch, aIso known as the Cape's Arch of Meridian, are situated in the extreme south-western comer of the African continent in the immediate vicinity of and adjacent to Cape Town, the capital of the Western Cape Province, one of nine provinces of the Republic of South Africa. Together with the Struve Arc in the Northern Hemisphere, already inscribed on the World Heritage List in 2004, the Cape Arch of Meridian and the related beacons, terminals, sites and structures in the Southern Hemisphere provided the scientific baseline for the measurement of the terrestrial surface of the earth and contributed significantly towards the collective knowledge of humankind of our own planet, the solar system and other stars and celestial phenomena.
An arc of meridian is an imaginary line, which runs true north-south, on the earth's surface that connects both geographic poles. It is used to indicate longitude. The scientific value of such a line is that, if the line is long enough (al least 70km or 43.4 miles) and surveyed with great accuracy, then the curvature of the earth can be measured. Add to that principle the accurate measurement of the latitudes (bow far north or south you are from the equator), at the two far ends of the line, and you means to the distance of the line by independent means to the physical measurement. This gives you an extra value to test measurement against. In other words: You can measure the curvature of the earth, and more than that, the size and shape of the earth.

Historic overview of the astronomical research
As is the case with other observational sciences, astronomical observations were collected and ad hoc hypotheses and original thoughts collated that gradually evolved into well-established theories over wider fields of knowledge. Over the centuries, physical laws underlying the observed phenomena were formulated and data collected to test and check theories, especially in astronomy. Since the number of objects that can be usefully subjected to a successfully established technique of accurate measurement is practically unlimited, especially since the development of computers and other high-tech instruments, astronomical research is becoming a highly specialised field. Spherical and gravitational astronomy are more advanced and it is in these branches of astronomy that some of the most important South African contributions have been made.
Some 4,000 years of visual observation provided an understanding of the heavens which was sufficient for the practical purposes of calendar-making, time-keeping, navigation, and the approximate prediction of the motions of the sun, the moon and planets. In the late 17th century much of this slow-accumulated knowledge was crystallized in Newton's laws of motion and of universal gravitation that rendered obsolete all earlier syntheses such as those of Ptolemy, Copernicus and Kepler. Showing that Newton's laws were sufficient to account for even the most minute details of the motions within the solar system occupied many of the great mathematicians throughout the 18th and 19th century and it was not till the 20th century that the necessity for refining Newton's theory by the concepts of relativity became apparent.
Before mathematical analysis can be applied to calculating epherimedes such as those required for the various nautical almanacs, the physical dimensions of the solar system and the 'initial' motions of its members must be known. The gradual refinement of the mathematical theory requires a corresponding improvement in the accuracy with which these quantities are determined, and vice versa. Thus from the 18th century onwards, professional practical astronomers, of which there were never very many, had a clear-cut if tedious task. They had to set up a background network of accurate star positions against which the motion of the sun, moon and the planets could be measured. A necessary part of this work is the determination of the size and shape of the earth and the numerical values of aberration, precession, nutation, polar motion, etc. which result from its complicated motions in space.
The modern pre-conceived idea that Europeans in the Middle Ages believed that the earth was flat, is largely a myth. By the 18th century it was general knowledge that the earth was approximately round. However, it had to be proved. During the 18th century the French National Academy set out to determine the shape of the Earth after it sent special expeditions to measure short meridian arcs in various parts of France, and later in other parts of the world. The Academy was of the opinion that 'France was the royal Arcanum of the sciences, and that England was a Nazareth from which no good or true thing could come', looked askance at any interruption to the continuation of the measurement of the arc of meridian, begun by Jean Picard by royal command of Louis XIV. The eIder Cassini completed Picard's triangulation between the 'most southern and most northern extremities' of France and obtained the result that the length of the degrees of latitude increased towards the equator. This meant that the earth was prolate, flattened at the equator rather than at the poles! Even though the Richer pendulum experiments at Paris and Cayenne supported Newton's oblate ellipsoid hypothesis, the French Academy of Science gave its support to the prolate hypothesis, but was unable to convince mankind and disprove the views of English origin. In order to resolve the matter, the Academy, in 1735, sent an expedition to Ecuador (then Peru) under the direction of Pierre Bougner to measure a degree of latitude at the equator and to compare it with the measurements made in France. The Bougner expedition's findings vindicated Newton's ideas. The Arc of the Meridian was measured at several other places, e.g. America, Russia and Germany, proving that the northern hemisphere was round. But the same had to be proven for the southern hemisphere. Thus with this in mind, the first serious astronomical expedition to South Africa took place from 1751-1753. Much of the work done at the Cape Observatory from 1820 onwards continued this initial scientific work.
In the 19th century it had become a problem for geodesists to solve as a by-product of their large-scale national boundary surveys: During the 21st century the most recent results depend on observations of special artificial satellites. Once the size and shape of the earth were known, the distance of the moon could be deduced by comparing its apparent positions in the sky as seen from two widely spaced observatories.
Once the distance to the Moon was known, it was possible to deduce that of the sun by a detailed analysis of the lunar motion, but such an indirect method assumes the truth of Newton's laws and did not carry the same conviction as a direct geometrical measurement of the distance of one of the nearer members of the solar system,

The first European astronomers and surveyors at the Cape
Knowledge of the stars surrounding the south celestial pole was virtually non-existent until Johann Bayer published his Uranometria in 1603. It was the first published atlas that covered the entire celestial sphere. Bayer introduced a new system of star designation, which has become known as the Bayer designation. Bayer was indebted for his knowledge of the southern skies to Petrus Theodori, assisted by Frederick de Houtman and Vechter Willemsz.
In 1685 a French diplomatic mission from the Court of Louis XIV at Versailles arrived at the Cape en route to the Kingdom of Siam at the request of King Narai (1656-1724). Their mission was partly as a counterweight to English and Dutch influences in and around Siam, partly as a means to facilitate French control over the burgeoning coastal trade and partIy to undertake mission work. The diplomatic delegation included six Jesuit priests. During their long sea journey, they came ashore at the Cape of Good Hope from 2-12 June 1685. They brought with them the best astronomical instruments available at the time. One of the French priests, Father Guy Tachard (1648-1712), said to have been a good friend of the Cape Commander Simon van der Stel, set these instruments up in an improvised observatory at the bottom of the Company's Gardens in Cape Town. He attempted to establish the longitude, but was unable to derive a useful coordination. Tachard and his assistants discovered that most of the stars shown on their charts of the extreme southern sky didn't exist at the marked positions, while many others were omitted altogether.
In 1705 Peter Kolbe arrived in the Cape, sent by a 'Prussian lord'. KoIbe brought with him letters of introduction from Nicolas Witsen, the Burgomaster of Amsterdam. His mission was to compile a description of the Cape and also to undertake astronomical and surveying research during the time that he worked at the Cape. However, towards the end of his stay the Governor of the Cape, Louis van Assenburgh, and his Council of Policy became annoyed with Kolbe as he did not pay duty and taxes and they asked Kolbe 'what he is going to do, because for some time now he has done nothing and not pursued his astronomical observations or done any burgher service. If he remains longer, he must be looked upon as a burgher or sent back to Holland.' Kolbe left the Cape in 1713. His observations were first published in 1719,

The Abbé de la Caille's expedition to the Cape
Given the political environment in Europe during the mid I8th century, it became increasingly important for the French ships to navigate the oceans of the southern hemisphere more accurately. And at the time, the stars were navigational aides, especially at nighttime. Thus it was not the land, but the sky that attracted the first distinguished scientist to spend more than a few weeks at the southern point of the African continent. At the time, the Cape was the most southerly accessible outpost of the known world where a private astronomer could establish an observatory. Therefore it was to Table Bay that the French Academy of Sciences sent the Abbé Nicolas Louis de Lacaille to set up his instruments to determine the position of the brighter stars in the southern sky.
Born on 15 May 1713 at Rumigny in the Ardennes, he first studied theology, but later changed his interest to mathematics and astronomy. Lacaille was employed by the University of Bologna's Observatory to survey the French coast from Nantes to Bayonne. In 1739, at the age of 27, Lacaille was appointed professor of mathematics at the Collège Mazarin in Paris, where he set up a small observatory. Lacaille was a protégé of Gian Domenico Cassini, head of the Paris Observatory. During 1740 he participated in a new survey of the arc of meridian in France. This was a departure from his principal interest of observations of celestial objects. By 1741 Lacaille was admitted to the French Academy of Sciences. In 1750 the Academy, growing ever concerned at the scantiness of astronomical data from the southern hemisphere, decided to take action and its choice fell on the Abbé. On 20 June 1750 permission was sought via the French East lndia Company for Lacaille to visit the Cape. He embarked, however, on 21 October 1750 before this permission had been granted. His journey, via Brazil, took nearly six months and he arrived at the Cape on board the Glorieux on 19 April 1751. He presented his imposing number of letters of introduction to the newly appointed Governor of the Cape, Rijk Tulbagh.
The Abbé lodged at 2 Strand Street, the house of Captain Jan Laurens (Louwrens) Bestbier, situated on the Table Bay side in Strand Street, just off the corner with the Heerengracht and Strand Street in Cape Town. He constructed an observatory in the courtyard (extending towards the sea) of the flat-roofed double-storeyed house, setting up his 28-inch long telescope. Here, according to David Gill, 'he laid the foundation of exact sidereal Astronomy in the Southern Hemisphere' and in the course of a period of less than 11 months, chartered the position of 9,766 stars, mostly in the southern hemisphere, using just his 1/2-inch refractor and compiled data which became the first catalogue of the southern stars to aid navigation. His Caelum Australe Stelliferum or ‘Star Catalog of the Southern Sky' was published partly in 1763 and completely in 1847 and is still considered to be reliable. The Philosophical Society (now the SA Royal Society) erected a commemorative plaque, designed by Herbert Baker, on the wall of the Lennon's Building (now demolished) to mark the spot of Lacaille's southern point of his arc of meridian in 1903. The plaque was reposition in 1977 on the ground floor of the new OId Mutual Building that was erected on the site.
Early in 1751, Captain Bestbier took Lacaille to visit the outpost of the Dutch East India Company, De Greene Kloof, the present-day Mamre. Here he climbed to the top of the Kapokberg, which he would use in his survey as an important beacon. On 1 November 1751 he again accompanied Captain Bestbier, this time to Stellenbosch where they attended a military parade. Lacaille was also a guest of honour of Govemor Tulbagh, together with the officers of the French, English, Danish and Dutch ships that were at anchor in Table Bay, during the centenary celebrations of the establishment of the Dutch kolonie on 8 April 1752. On 19 May 1752 he visited the Drakenstein and commented on the number of farms in the valleys where a large number of vines were planted. He also noted that only the old descendants of the Huguenots could still speak French. Lacaille (according to Picard) also aired his opinion in that he got to know three intelligent men in Cape Town: The first being the Governor, Rijk Tulbagh, the second the Secretary of the Council of Policy, Du Grand Prez, and the third Nicolaas van Dessin, Secretary of the Orphan Chamber, whose books later launched the first library in Cape Town.
In 1755 Lacaille's Sur les étoiles nébuleuses du ciel austral was published by the Royal Academy of Sciences, a catalogue of 42 southern nebulae or Southern Deep Sky objects for the French Army (32 of which are real, among them are 24 original -including the Tarantula Nebula NGC 2070 in the Large Magellanic Cloud, and at least 2 independent rediscoveries). His catalogue graded for the first time the southern stars according to brightness, as well as revealing a number of new constellations. Lacaille also named 15 of the 88 constellations in the sky: instead of the classical nomenclature of Greek and Roman mythology, he used scientific instruments as the inspiration for his new titles, including naming one constellation Mons Mensoe (meaning 'Table Mountain' -to this day it is the only constellation named after a terrestrial feature on Earth. Lacaille thus laid the foundations of southern hemisphere astronomy and was the predecessor of all the later astronomy pioneers, e.g. Thomas Maclear, Sir John Herschel and David Gill. Although Lacaille's achievements were later vitiated due to the lack of adequate instrumentation for his basic work, Maclear and Herschel acknowledged his survey of the southern sky and it is generally held by astronomers to have been the true starting-point of modern scientific work in this field. His diary and observations was published in 1763 as Journal historique du voyage fait au Cape de Bonne-Espérance.
Lacaille also made painstaking observations of the moon and planets, and determined more accurately than ever before the longitude of the Cape, a signal service to navigators. He also measured the distance between the earth and Mars, being 131 500 000 km (81 710 310 miles), the distances to the moon and closer planets and established the exact longitude at the Cape using observations of the satellites of Jupiter.
Lacaille completed his observations in August 1752. He was, naturally, extremely interested in the shape of the earth and the forced extention of his stay al the Cape for six months gave Lacaille an opportunity to measure an arc of meridian. At the time, measurements in the northern hemisphere indicated that it was not a sphere but oblong in shape, i.e. slightly flattened at the poles. Lacaille was keen to discover whether observations in the southern hemisphere would confirm this finding as the measurement of the Arc of Meridian was important to determine the size and shape of the earth. He carefully planned his survey and obtained the approval of the Govemor, Rijk Tulbagh. Tulbagh instructed both officials and inhabitants of the Cape to assist Lacaille in his endeavours. It also seems as if Lacaille was well liked by the Cape society whom he met. Denis Diderot, having met Captain Robert Jacob Gordon in The Hague in 1774, recorded: 'Mr Gordon... praised the truthfulness and accuracy of Monsieur l'Abbé de Lacaille, who he added was not often mistaken. He was accorded great respect by the Dutch of the country who could not understand how a man could have come from so far, encountering a thousand different dangers, just for the advancement of astronomy and without any design of ambition and wealth.
In August 1752 Lacaille made a preliminary field trip to select a suitable site for the northern point of his proposed arc; the southern point being his own observatory in Cape Town. This later proved to have been an unfortunate choice. His choice fell on the farm Klipfontein for the northern point.
Governor Ryk TuIbagh provided assistance to Lacaille for his survey of the arc of meridian. Captain Bestbier supplied slaves, wagons and carts with oxen and horses for the transport of his instruments and equipment whilst Captain EB Muller, an artillery officer who was also the engineer at the Castle, was instructed to accompany Lacaille. A man named Poitevin, who possible came with Lacaille from France, accompanied them. On 9 September 1752, Lacaille and his party set out for the farm Klipfontein, northwest of Piketbcrg, to establish the northern point of an arc of meridian nearly 1¼ degrees in length at latitude 33°18'S. Four days later they arrive at the Berg River near Rietkloof. It took them more than two-and-half hours to cross the river. They slept at Groen Fonteyn and reached Klip Fonteyn the next day.
His fundamental baseline, 13 km or eight mile in length, (approximately 1¼ degrees in length), was measured on the Darling Flats, using wooden rods. From each end of the baseline he measured the angles to signals he had set up on the top of the Kapokberg and Kasteelberg (near the present-day Riebeek Kasteel). During October 1752, the party was stranded without tents or bedding for eleven days on Kasteelberg due to bad weather. The beacon fires on the Piquetberg, which were to be used as fixed points, were not kept constantly alight Captain Muller, in a request to the Governor dated 11 October 1752, required a few more days of leave.
Lacaille calculated the distance between his points that he selected; he could observe both the house in Cape Town and the KIipfontein farmstead from the mountaintops and he calculated the distance between the KIipfontein and Cape Town points as being 137 km (85 miles). Then, by triangulation and signal fires, he measured the 137 km arc of meridian between Table Mountain and Aurora. The survey was made up of two large triangles with the common side along the line stretching from the Kapokberg to Kasteelberg, the southern point being his own observatory in Cape Town and the northern point the farm Klipfontein, north of Piquetberg. Two secondary triangulations were determined from a baseline between Uylekraal and Vygekraal (north of the present-day Darling). While he was busy with his survey, it is said that Lacaille walked the distance between the Kasteelberg, the farm KIipfontein and Cape Town three times! A report (Darling) by an aged Letchie Schalkeveck indicated that the signal fires that were used were 'so large and brilliant that those of Riebeeck Casteel were visible from Klypfontein ... with the naked eye at night'.
Despite his painstakingly exact work to measure this arc of meridian, the Abbé de la Caille did not measure the deflection caused by gravity pulling the plumb bobs towards Table Mountain, Kapokberg and Riebeeck Kasteel, which caused errors in the results of his triangulation. When Lacaille had previously measured the arc of the meridian in France and other European countries, he found the Earth to be oblate. This agreed with Newton's theory, but Cassini, under whom he worked, did not believe it. Lacaille was thus astonished and disappointed by the results of the survey that he had done at the cape, which made the southern hemisphere appear to he pear shaped! In addition to the errors caused by plumb bob measurements being distorted on or near the mountains, it was only discovered recently that the measuring rule supplied to de la Caille was about ¼ of an inch in 6.4 feet (a toise) too long, which was not his fault.
Not content with these outstanding achievements, Lacaille involved himself in much other work, including a survey of Hout Bay and the measurement of the height of Table Mountain, which he did as a favour for the Governor, Rijk Tulbagh.
On 8 March 1753 Lacaille left the Cape on board the French ship Le Puisieux bound for Mauritius to determine the exact position of Mauritius and Reunion. He later returned to the Mazarin College in France. In the light of what he achieved, it is incredible that he actually spent less than two years at the Cape. After his return to France in 1754, he worked alone in compiling his data, and overwork apparently caused his death on 21 March 1762 in Paris aged 48. His contributions to science were among the most valuable made during the 18th century. His Coelum Australe Stelliferum was published posthumously in 1763. In addition to his astronomical investigations, his diary, Journal historique du voyage fait au Cap de Bonne-Espérance (l763), is of considerable interest. The University of the Witwatersrand possesses one of Lacaille's original observing books. Other original manuscripts are kept in the Bibliothèque de l'Observatoire de Paris.
Other astronomers visited the Cape after Lacaille's departure: Charles Mason and Jeremiah Dixon, two English engineers, visited Cape Town in 1761 specifically to observe the transit of Venus from a temporary observatory in the Concordia Gardens, a public pleasure garden that was modelied on London's Vauxhall and Cremome Gardens. The Concordia Gardens were situated behind the present-day St Mary's Cathedral.
Wales and Bayly, the astronomers of Captain James Cook's second voyage, also made observations from the Concordia Gardens during their visit to the Cape late in 1772.

The visit of George Everest to the Cape in 1820
George Everest, later the Surveyor-General of India, visited the Cape in 1820 on his way back to lndia. At the time of this visit, he already had extensive experience of the effect that mountains have in surveys that he undertook in lndia and on the island of Java.
Everest investigated the circumstances of Lacaille's arc and inspected his beacons and postulated that the gravitational attraction of mountains (in this case Table Mountain and the Piketberg) could have caused anomalous disturbances on Lacaille's plumb line readings, causing the confusion. He realised the mistake that Lacaille made and strongly recommended that a survey of new triangles, extending over a much longer arc, be undertaken. This advice was taken up in the instructions of the Admirality issued to Thomas Maclear to prove it.
The next major event was the establishment of the Royal Observatory in 1820.

The new Royal Observatory at the Cape of Good Hope
After the victory of the Royal Navy during the Napoleonic Wars the Admiralty in London began contemplating the establishment of an astronomical observatory ill the southern hemisphere. For this, the Cape Colony was the obvious place. The building of the new Royal Observatory at the Cape of Good Hope was also considered to be a major development in establishing a modern scientific institution in Africa, the first since the burning of the Library at Alexandria: However, it began in a very humble way.
On 20 October 1820 the Commissioners of the Admiralty decided to proceed with the plan at once and the Cape was chosen as the preferred site. The Engineer to the Admiralty, John Rennie, was commissioned to prepare a design for it, but it seems likely that the drawings (signed by John Rennie and dated 1 March 1821) are actually the work of his younger son, also John Rennie, for the eIder Rennie is not known to have engaged directly in any architectural work. On the other hand, his son, the later Sir John Rennie., was influenced by the neo-classical revival and his Royal Victualling Yard at Stonehouse, near Plymouth, is regarded as 'amongst the first works of the engineer-architect in England. The younger John succeeded to the post of Engineer to the Admiralty upon the death of his father in October 1821, so that he was clearly in the position, only a few months before, to have been entrusted with the designed of the Observatory. Rennie was an adherent of the Greek Revival school of architecture and his observatory was the first example of this style in South Africa. According to Lewcock, the Royal Observatory has also the distinction of being, since the demolition of the old St George's Cathedral in Cape Town, the finest example of Greek Revival architecture in the country.
The instruments for the Royal Observatory escaped being dumped on the beach of Table Bay only because the President of the Burgher Senate, Mr Van Breda, volunteered a room in the Granary. Observations began from a prefabricated wooden hut, intended for the British Settlers in Algoa Bay, set up in the back garden of a rented house. This property, at 13 Kloof Street, was known as the garden Rozenhof. Here Fallows began observing the southern stars. The results of his early observations were published in a catalogue of 274 'principal fixed Stars' in 1824.
After a search of two years, a vacant piece of land, forming a slight knoll between the Liesbeeck and Black River, referred to as 'Snake Mound', was selected for what has grown into a small campus of related buildings.
Building work only started in 1825, because the Admirality Office mislaid the original plans and these had to he redrawn. There was a shortage of suitably qualified and experienced stonemasons at the Cape and the teak required had to be purchased in such a manner that it would not raise the suspension of the merchant! The contractor for the new building was John Skirrow, the Clerk of Works, who was seconded from England especially to execute the contract It was built of plastered brick, with a roof that required 30 tons of lead. Huge stones for mounting the permanent instruments were also required. The structure was only completed in 1827.
The Royal Observatory building has a wide H-plan, with its entrance in the 'crossbar' behind a Doric four colonnaded temple-front. The central block contained most instruments; the wings, one-and-a-half-storeyed though not much higher than the central bock, the living quarters for the astronomer and his staff, except for the front rooms which housed two more telescopes (these telescopes and their domes, mounted on the roofs, were removed at an early stage because of the lack of stable foundations. The projecting rooms to the front have large windows-three-pane-wide sashes flanked by coupled two-pane sashes -set in slight recesses with arched tops repeating the one-time metal telescope-domes. AIl roofs are flat, with plain cornices and slightly stepped parapets. An intended central dome was replaced with an octagonal lantern loosely based on the 'Tower of the Winds' in Athens. It, too, was later removed. Lewcock is of the opinion that the plan is thus essentially Palladian, but that there is a resemblance to 18th century architecture ends. The building is notable for its stark stucco surfaces defined at the bottom by small plinths and at the top by plain Doric cornices. All the emphasis of the main façade is focussed on the central portico, resembling a Greek Doric temple.
The first Director of the Royal Observatory at the Cape was the Reverend Fearon Fallows, who oversaw the building of the main structure. Fallows died in 1831, the victim of scarlet fever and is buried in front of the building. Thomas Henderson, who brought some fame to the Royal Observatory, though he stayed for only two years and disliked the place, replaced Fallows.

Maclear remeasures Lacaille's Arc of Meridian
Thomas Maclear, a surgeon turned astronomer, was appointed to the directorship of the Royal Observatory in 1833. Although until then he had been purely an amateur, Maclear had already been admitted as a Fellow of the Royal Society. Born on 17 March 1794 at Newton Steward, County Tyrone, Ireland, Maclear, a medical doctor by training, became an astronomer and land surveyor.
He came to the Cape on the Tam O'Shanter with his wife Mary, five daughters, a governess, a nursemaid and a manservant/assistant, Thomas Bowler, who became a well-known artist in Southern Africa. The entourage arrived at the Cape on 6 or 7 January 1834 where he took up his appointment and held the position of Astronomer Royal for 26 years.
Maclear was send to the Cape with two specific tasks: He was firstly tasked to prepare a catalogue of southern stars and was entrusted with the building up of the young Observatory and organizing its routine astronomical, meteorological and magnetic observations. From 1834 to 1838 he worked with John Herschel, surveying the southern sky. However, the survey never quite got completed.
Maclear also expanded the time service by firing a cannon from Signal HilI at 9 p.m. In 1836 a time-ball was erected at the Observatory. The first assistant astronomer at the Cape, appointed in 1835, Charles Piazzi Smyth (1819-1900), and a close friend of Charles Bell, assisted Maclear until Smyth was appointed Astronomer Royal for Scotland in 1845.
Maclear's second task was to re-measure Lacaille's Arc of Meridian. Due to the influence of the magnetic field of the mountains around the Cape on his instruments, Lacaille's measurements in the mid 18th century indicated that the earth would be pear-shaped. Despite the respect that the scientific community had for Lacaille, the result of his survey and observations put the scientists in a conundrum. Thus, some eighty years later, the British Admiralty wanted a conclusive answer and the mystery solved. From late 1836 to 1847 Maclear and his assistants were engaged in the work on the Arc of Meridian: Mac1ear decided to use Bradley's Zenith Sector to re-measure the Arc of Meridian to ensure very accurate latitude measurements at each end of the arc. Maclear had to modify the Lantern on the Observa1ory roof in order to erect the Zenith Sector.
On 26 November 1836 and with the permission of the Governor, Maclear started by laying out a baseline, 1050 feet in length, on the northern edge of the Grand Parade, which he accomplished with a surveyor's chain. Each end of this baseline was marked with an unserviceable cannon, its muzzle plugged with lead and a brass pin driven into the centre, sunk vertically into the ground. One of these cannons was recovered during the excavations on the Golden Acre site. Piazzi Smyth recorded these proceedings a sketch that contains much social comment rather than technical information. Three days earlier, on 23 November 1836 he had set up signals at the King's Blockhouse against Devil's Peak
Maclear also set out a more extensive baseline in the grounds to the north of the Observatory. This baseline, 2919.365 feet in length, was completed in November 1837 and Piazzi Smyth made two fine sketches illustrating the work carried out during the setting out of this baseline. Maclear also took measurements of angles at each end of the base to enable him to connect accurately the positions of Lacaille's observatory in Strand Street, the Royal Observatory, and Sir John Herschel's observatory in Claremont (where a baseline 516 feet in length in the avenue of the Feldhausen estate was laid out.
In November and December 1837 Maclear used his measuring rods to re-measure the Parade Ground Baseline using more accurate instruments. This baseline was provided for land surveyors so that they could compare their chains with an accurately determined distance. The laying out of this baseline created great interest in Cape Town and Piazzi Smyth recorded this scene in another sketch.
Early in 1838 Maclear moved the Zenith Sector to the site of LacailIe's lodgings at 2 Strand Street, now owned by Mrs De Win and positioned it as near as possible to Lacaille's original site. After making observations during the first three weeks of February 1838, Maclear moved the instrument to a site on the northern face of Table Mountain at the bottom of Platteklip Gorge. From 24 February to 13 March 1838 he experimented to see by how much the mass of Table Mountain affected the latitude determination.
With the local baselines and surveys completed, Maclear and his party set out on 15 March 1938 for the northern end of Lacaille's Arc at Klipfontein. They were not able to identify the exact position of Lacaille's observation station and they erected the Zenith Secyor on a nearby site on the same farm. The Zenith Sector was housed in a 4m high tent, specially manufactured for this purposed, during the expeditions in the veld: much trouble was caused by high winds and, later in the survey, freezing rain and snow. By 22 April 1838 the observations at Klipfontein were completed and the Sector was returned to Cape Town. There it was erected in the Rogge Bay Guard House near to Strand Street, and protected from the wind. On 30 June 1838 it was moved to the Observatory.
Of the northern terminal, Maclear wrote in his Journal: 'The station may he recovered at any future lime . Besides, a pit was dug in the corn-floor, under the axis of the sector, three feet and a half deep, where the rock was met with. A hollow was chiselled in the rock to receive a quart bottle, containing the folllowing memorandum, written in large round hand:
''Bradley's 13½-feet zenith sector was placed over this spot (supposed to he the north extremity of La Caille's arc of the meridian) for the purpose of verifying the astronomical portion of that work, on the 27th day of March, 1838. The observations began on Wednesday, the 28th, and continued to the 21st day of April, when the instrument was taken down. The party consisted of Thomas Maclear, H. M Astronomer; Lieut. Williams, Royal Engineers; J Smith, Sergueant, Royal Engineers; Sharpe, Gunner, Royal Artillery; Joseph Gibbs, Carpenter and Labourer to the Royal Observatory, Conrad Engelbraght, Johnny Wallace, Servants. Signed by Thomas Maclear and John Williams."
On the other side of the paper was written:
"Over this there is a stone 1ft11 in long, 13½ inches in breadth, and 5½ inches deep, with the letters B. S. 1838. Whoever disturbs this is requested to replace it with care, and to notice the circumstance."
Maclear noted that the 'scroll was inclosed in a piece of blotting paper, and then covered with a thick coat of sealing-wax. The bottle being warmed, the seron was introduced, and the cork dipped in tar, and placed in the hollow cut out of the rock at the bottom of the pit, and covered over with the stone above described, over which earth was rammed down firm, and the surface smoothed as before. Mr. Lambritz, nephew of Jerrit Cotsee, and Hendrick Thiark, the proprietor, were made acquainted with the object of the memorandum.'
According to an unpublished letter dated 5 June 1986 and written by Tannie José Visser (née Coetzee), her brother witnessed how the threshing floor was dugged up due its poor state either in 1919 or 1920. A 'brass pin mounted in a heavy metal cylinder had been found, the whole set in a circle of flat stones. The cylinder had been removed and subsequently lost, but the stones had remained undisturbed. Maclear researched Lacaille's account and he came to the conclusion that there had to have been two farmhouses at the time of Lacaille's visit, one occupied by Oker Schalkeveck and the other by the owner, Cornelius Cotsee. Lacaille and his assistants, together with their instruments were accommodated in the small granary of Cornelius Cotsee. Letchie Schalkeveck recalled: 'The Abbé observed the stars with his instruments in the granary (an aperture having been made in the thatched roof for the purpose) until the day the fires were lit.' She also recalled Lacaille's small dog named Grisgris. A descendent, Gerrit Corsee, recalls that Cornelius Cotsee's house was demolished and a threshing-floor and a shed had been built on its foundations. The ruins of the granary were excavated by sappers to a depth of two feet and the instruments that Maclear used was then set up on the threshing floor. Maclear recalled: '... before the foundation of the granary was discovered; and as the place was comparatively convenient, and the influence of the surrounding masses nearly common to both, l went on where I began.'
The exact position of the northern terminal was only established on 3 July 1990 when, at the request of the then National Monuments Council Prof. Hilary Deacon of the Archaeology Department of the University of Stellenbosch, together with Mr. Boet Roussouw, Director of Geodetic Survey section of the Trigonometrical Survey, Mr. Keith Graham of the Office of the Surveyor-General and several other people Undertook an archaeological investigation based on data gained from Maclear's notes by Mr Graham. A large sandstone slab with the date 1838 inscribed on it was found at a depth of about 500mm together with an English black glass bottle below it. The bottle was left intact, but the stone slab was removed for study purposes and housed at lziko Museums of Cape Town. The Council of Iziko Museums decided that the stone be reburied at its original location on the farm. This is in line with the conservation principles of keeping materials in the place of origin and the permit issued by the former National Monuments Council on 29 June 1990.
A proposal to expand the work of the Royal Observatory at the Cape over the next ten years was sent to the Royal Observatory in Greenwich. This request was apparently successful as instruments that were required for the re-measurement of Lacaille's Arc arrived at the Cape when the Second Assistant, William Mann, disembarked in Cape Town on 22 October 1839. These instruments assisted immensely with the work from 1840-1847.
Maclear's triangulation measurements were made with the most accurate theodolites available: One, contributed by Sir Francis Beaufort, was never returned and is now housed in Iziko Museums of Cape Town. Triangulation of the Arc required a baseline and extensive surveys. As Lacaille's baseline was no longer discernable and could therefore not be checked, a new baseline, eight miles in length, was laid out as near as possible to that of Lacaille's. The work started on 21 October 1840, but took longer than expected and was only completed by 5 April 1841. Maclear and Piazzi Smyth made all the measurements themselves -and supervised the operations whilst being assisted by Captain Alexander Henderson and eight other Royal Engineers sent out from England for this purpose as well as 14 men from the Cape Garrison. Further assistance came from some of the survivors of the wreck of the Abercrombie Robinson that ran aground on 28 August 1842 and who was employed to assist. Charcoal from Lacaille's signal fire on Riebeek Casteel was collected by Maclear in 1841 and is preserved al the South African Astronomical Observatory.
The eastern and western terminals were marked. Maclear wrote that he marked the western point with ' ... an iron pipe which a brass plug is fixed with lead, in the centre of the brass a platinum wire is inserted, and its end is polished off: upon this end is the dot.' Later each of these terminals was encased in a 3m high stone pyramid.
Maclear also later extended the primary base line, after he had received funding from the Admiralty, to the Orange River. The Zenith Sector was conveyed to the Heerenlogement Berg and the Kamiesberg in 1842 and in 1844 to Zwart Kop (south of Simon's Town) and to Cape Point. Having completed the work with the Zenith Sector in January 1845, it was sent back to England on 1 May 1850 where it is still kept in the Royal Observatory at Greenwich. The baseline set out by Maclear remained the primary base line on which all South African geodetic surveys are based, being only recently superseded by Hartebeesthoek TRF 91 Epoch 94 WGS 84. The results of this re-measurement and extension of his triangulation, carried out under the auspices of the British Admiralty, showed that a degree in latitude 35°S was shorter than the French measurement of one degree in latitude 40°N. Maclear's results thus supported the idea of an oblate earth. At least two of the crew died during the ten years it look to complete the measurement.
With the help of his assistants Piazzi Smyth and William Mann, Maclear found an error of 14 feet in the length of the baseline measured by Lacaille. He published his findings in his two-volume Verification and Extension of Lacaille's Arc of the Meridian al the Cape of Good Hope in 1866.
By 1853 Cape Town has expanded so much that the ships in the harbour could not see the time ball on the Observatory grounds anymore. Two new time balls were added to the time service, one at Signal Hill and the other at Simon's Town. By 1861 telegraph lines were installed in the Cape Colony and the drop of the balls were now done automatically electrically from the Observatory. In 1865 another time ball was added to the system, in Port Elizabeth, 750 km (±500 miles) distant.
Maclear erected a stone cairn, a trigonometrical beacon, known as Maclear's Beacon, in 1865 on the highest point of Table Mountain near the north-eastern face and it can be seen as symbolising that the earth is oblong in shape. Scientifically, the re-measuring of the Arc of the Meridian was the most important project Maclear undertook. With a bit of poetic licence it can be said that Maclear finally proved that the earth is oblong in shape.
Maclear received international acclaim for solving the riddle caused by Abbé de la Caille in the mid 18th century, including a knighthood from Queen Victoria bestowed on him in June 1860, thanks to the influence of Sir John Herschel. Lady Maclear passed away on 27 July 1861 and she was buried in the grounds of the Royal Observatory. In 1867 Sir Thomas Maclear received the Lalande Medal from the French Academy of Science, and in 1869 the Gold Medal of the Royal Society. Maclear established and served on the Meteorological Commission for South. Africa and the Commission of Standards for Weights and Measurements for South Africa. He also assisted in the establishment of lighthouses around the Southern African coastline.
Maclear's geodetic work led to the setting up of the official Trigonometrically Survey Office of South Africa (based in Mowbray, Cape Town). His work provided a sound foundation for a trigonometric survey of the then Cape Colony, which extended in later years into Africa because Maclear set the standard length measure. Maclear was very interested in the exploration of Africa and was a close friend of David Livingstone. Maclear taught Livingstone to use a sextant and he reduced many observations of position, made on Livingstone's journeys. Livingstone also presented Maclear with a rhinoceros hide walking stick, still in the possession of the Observatory.
Maclear retired in 1870 and his eyesight deteriorated and he lost his sight by 1876. He died on 14 July 1879 and was buried beside his wife in the grounds of the Observatory. The town of Maclear, as well as Cape Maclear, was named after him as much of his public-spirited service to the community as for his prowess in astronomy. He died on 14 July 1879 in Cape Town.

Sir John Herschel visit to the Cape
Sir John Herschel's visit to the Cape lasted only between 1834 and 1838 and he held no official. appointment during this period; nevertheless his contribution to the fame of the Royal Observatory and South African astronomy could hardly be over-emphasized. Born on 7 March 1792 in Slough, Buckinghamshire, the only child of Sir William Herschel, the discoverer of Uranus. Elected a Fellow of the Royal Society of London at the age of 21 for his work in mathematics, John Herschel quickly turned his attention to astronomy. In 1820 he was among the founders of the Royal Astronomical Society. Herschel made important contributions to chemistry and the physics of light and particularly to mathematics, for which he was awarded the Copley Medal of the Royal Society in l821. He served as secretary of the Royal Society from 1824-27. He married in 1829 and in 1831 he was knighted.
In 1833 he completed the re-observation of his father's double stars and nebulae in the northern hemisphere. Sir John's sense of obligation to complete his father's work in astronomy led him to consider a journey to the southern hemisphere to survey the skies not visible in England. In 1832 he began planning his expedition and in November 1833, Sir John, his wife Margaret and their three small children, together with Sir Benjamin and Lady D'Urban as fellow passengers, set sail for the Cape of Good Hope aboard the Mountstuart-Elphinstone. On board also was a large 20-foot reflecting telescope for observing faint nebulae. The Herschels arrived on 15 January 1834 within ten days of their friends Thomas Maclear and his wife.
The Herschel family established their home at Feldhausen, a Cape Dutch farmhouse situated southeast of Cape Town that later became known as The Grove. Sir John set the telescope up in the garden of the estate and spent years of intense scientific activity, the clear southern skies allowing much more rapid progress in observing than was possible in England. Sir John helped Maclear through a difficult period at the Royal Observatory and assisted him with geodetic surveys and tidal observations. He sketched flowers and scenery, helped establish a meteorological committee in Cape Town, experimented with solar cookers and invented an instrument for measuring heat radiation. He also found time to take an interest in public affairs and, with Colonel John Bell (the Colonial Secretary at the time and uncle of Charles Bell) and John Fairbairn (the newspaper editor and proprietor) proposed a scheme for a state system of education in the Cape that was implemented.
A technician, John Stone, assisted Sir John with his observations. During his stay Sir John charted the Argo nebula, placing 1,203 stars in it; he catalogued 1,163 objects in the magellanic clouds; discovered and tabulated nearly 2,000 other-nebulae and clusters; discovered 1,202 pairs of double stars and observed Halley's comet from 28 October 1835 to 5 May 1836. On his departure in 1838, he placed a small granite cylinder on the spot where his six-metre telescope had stood.
The importance of astronomical observations during expeditions was considered very important, as was illustrated when Dr Andrew Smith included Charles Bell as second draughtsman in his party on the expedition into the southern African interior in 1834. Maclear, in his recommendation of Bell, described him as being 'fit for anything'. Bell followed the brief in the Instructions Addressed to the Director by the Committee of management to 'make a faithful record of its route, which can only be done by the aid of astronomical observations made with due regularity and precaution.' And when Bell received instructions in 1840 from the assistant surveyor-general of the Cape, Willem Frederik Hertzog, to investigate the establishment of a new magistracy in the Hantam Mountains north of Cape Town, be also received the following order: ‘Finally you will both going and in returning put yourself in communication with the Astronomer Royal for the purpose of obtaining from that Gentleman and for recording by notes and sketches -all such information desirable from the measurements on which Mr. Maclear is now engaged., as shall be requisite in proceeding hereafter with the general Trigonometrical survey of the Colony.' These instructions clearly indicated how important the won on the Arc of Meridian was that Maclear was engaged with at the time.
When the Herschel family boarded the Windsor bound for England on 11 March 1838, Sir John had recorded the locations of 68,948 stars and had amassed long catalogues of nebulae and double stars. He had also described many details of the Great Nebula in the constellation Orion, as well as the Magellanic Clouds-actually two galaxies visible only in the southern Hemisphere -and bad observed Halley's Comet and the satellites of Saturn. Upon his return he was made a baronet (during the coronation of Queen Victoria in 1838) and was lionized by the scientific world. He is buried in Westminster Abbey.

David Gill extended the surveying of large tracks of southern Africa
Born on 12 June 1843 in Aberdeen, Scotland, Gill was educated at the University of Aberdeen. In 1872 be became director of James Ludovic Lindsay's private observatory near Aberdeen. From there he undertook expeditions to Mauritius in 1874 as part of Lord Lindsay's Transit of Venus expedition to observe this phenomenon. Accompanied only by his wife, he visited Ascension Island in 1877, when Mars was in opposition. His measurements of Mars's position as it neared the Earth enabled him to roughly calculate the solar parallax. In 1888-89 he carried out, with the cooperation of other astronomers, a program of intensive observation of selected minor planets with the heliometer. This led to the first determination (1901) of the solar parallax with modern accuracy.
As Royal Astronomer at the Cape of Good Hope from 1879 to 1907, he photographed the sky within 19° of the south celestial pole in great detail. From these pictures, the Dutch astronomer J.C. Kapteyn compiled the Cape Photographic Durchmusterung, a catalogue of nearly 500,000 stars.
Contributing to the determination of the size and shape of the earth, and thus also a vital step in evaluating the distance to the sun and the stars, Gill initiated and oversaw various large-scale surveys of southern Africa One of his objectives was a complete triangulation of the 30th east meridian from South Africa to Norway, the longest arc of meridian measurable in the world. He saw his work started, but did not live to see its completion, after the Second World War.
Gill realized the need for maps in the Cape Colony and hence for a geodetic survey. When Gill put a proposal to this effect before the Governor, Sir Bartle Frere, the project was approved. After gold was discovered on the Witwatersrand in 1886, Gill felt the need to press the survey further into the Orange Free State and the ZuidAfrikaanse Republiek, and persuaded the Presidents of those Boer Republics of this need. Gill was knighted in 1900. Work on the extended survey was sporadic, for financial reasons, and was completed only in 1902 by the Royal Engineers, after which it was also extended into the area controlled by the British South African Company (the present-clay Zimbabwe). He died on 24 January 1914 in London.

The completion of the survey of the 'great arc of meridian' on the African continent
Many years later the efforts of Gill and others were crowned by the completion of the survey of the 'great arc of the meridian' (the 30th meridian east, representing a distance roughly equal to that between Durban, 31°S, and North Cape, Norway, 71°N), which is the longest arc of meridian measured by triangulation on earth.
The final gap in the triangulation chain was closed in 1955 when American surveyors extended the Ethiopian survey control framework as part of a geodetic aid programme facilitated by the International Association of Geodesy. The Director of Colonial Surveys and survey adviser to the British Government in the years following World War II, Brigadier Martin Hotine, assisted in the observation and computation of the great arc through the then British colonies of Central and East Africa.

Beacons, terminaIs, sites and structures associated with the Cape Arc of Meridian
The Beacons, terminals, sites and structures associated with the cape Arc of Meridian are:
1. The plaque commemorating the southern terminal of Abbé de la Caille (now situated in the Old Mutual Building), Cape Town and the cannon marking the baseline along the northern boundary of the Grand Parade set out by Thomas Maclear.
The original Cape double-storeyed flat-roofed house where Abbé de la Caille lodged at No 2 Strand Street in Cape Town no longer exists, but early photographs in the South African Library and in the Western Cape Provincial Archives exists showing his calculation drawn on the courtyard wall.
This site, originally in the courtyard of the house, marked the position of the southern terminal of Lacaille's Arc of Meridian.
A canon used by Maclear on the northern boundary of the Grand parade to set out a baseline as a measurement for local land-surveyors was excavated during the construction work on the Golden Acre in the 1980s. It has been restored and repositioned on site.
2. Maclear's Beacon, Table Mountain
Thomas Maclear erected a stone cairn, being a trigonometrical beacon, and known as Maclear's Beacon, in 1865 on the highest point near the north-eastern face of Table Mountain. Maclear's Beacon is the highest elevation (1,113m) of Table Mountain (Table Mountain is a provincial heritage site and is inscribed on the World Heritage List as part of the Cape Floristic Protected Area)
3. The Eastern Terminal Point Beacon of the Zwartland Baseline of Maclear's Arc of Meridian
The Eastern Terminal Point Beacon of Maclear's Zwartland Baseline, laid down in 1840, is situated on the farm Eendrag on the Darling Flats between Hopefield and Malmesbury. Several of the beacons that Maclear erected, some that were stone pyramids, were later replaced by standard concrete pillars and incorporated in the trigonometrical survey of South Africa. The Eastern Terminal Point Beacon forms part of the Zwartland baseline survey (a declared provincial heritage site).
4. The Northern Terminal Point Beacon of Maclear's Arc of Meridian, Klipfontein, Piketberg District
The Northern Terminal of Maclear's Arc of Meridian measurement is a point in the centre of a threshing floor of the farm Klipfontein, just north of Aurora in the Piketberg District. It represents the beginning of South Africa's primary geodetic survey, which still forms the framework for topographical mapping and all subdivisions of land. The exact position of this terminal, forming part of a threshing floor, was established in 1990 when a large sandstone with the inscription '1838', as well as a black glass bottle were excavated by the archaeologist Prof. Hillary Deacon of the University of Stellenbosch. A stone cairn has since been erected to mark the position of the terminal (a declared provincial heritage site).
The Northern Terminal of Maclear's Arc of Meridian, together with the threshing floor, situated on a portion of Portion 9 of the farm Klipfontein 103 in the Administrative District of Piketberg, in extent 330 m3, and surveyed as per Surveyor's Diagram SG297/94, dated 16 February 1994 and filled in the Office of the Surveyor-General in Cape Town, was declared as a national monument in 1994 (Government Notice 1085 published in the Government Gazette No15796 dated 17 June 1994. It is now a provincial heritage site.
6. The Royal Observatory of the Cape of Good Hope, now known as the South African Astronomical Observatory, Observatory, Cape Town
The Royal Observatory was designed by John Rennie in 1821 and building started in 1825. The Royal Observatory was declared as a national monument in 1980 (Government Notice 2080 published in the Government Gazette No7259 dated 17 October 1980. It is now a provincial heritage site.
7.The Time-ball Tower, Cape Town
The Time-ball Tower off Portswood Road in the Victoria and Alfred Waterfront in the Cape Town harbour was constructed in 1883. This structure was used as a repeater station for harbour signals between the Royal Observatory and Signal Hill. This square, three-storey brick tower with recessed fields at second-floor level and windows at third. A mast with a time-ball tops its pointed copper roof.
In 1895, it was raised from 5.18m to 10.36m. The ball, which was band operated at first, was electrified in 1903 and the mechanism was replaced in 1934 to be operated by radio signals. The time-ball tower is a provincial heritage site.
Gabriel Pagan Architects restored the structure in 1990. This site is also closely related with the Greenwich World Heritage Site. It is reportedly one of three remaining time-ball towers in the world, i.e. in Greenwich, Great Britain (included in the Maritime Greenwich World Heritage Site) and another in New Zealand.
8. The Herschel Monument or Obelisk at Grove Primary School, Bishoplea Road, Claremont, Cape Town
In the grounds of the Grove Primary School that occupies the site of the old Cape Dutch homestead Feldhausen, where the Herschel family lived during their sojourn at the Cape, there stands an obelisk indicating the site of Sir John Herschel's telescope.
Sir John Herschel had made a considerable impact on the Cape society and Maclear proposed that a permanent monument be erected to commemorate his visit. There was a difference of opinion as to where this memorial was to have been erected: One faction proposed the Grand Parade, whilst Maclear argued that it should be placed to mark the centre of the Herschel telescope at Feldhausen.
When Herschel sold Feldhausen, he retained a piece of land, 36 feet in diameter, centered on the granite cylinder, and this remained in the family until it was transferred by a great-granddaughter of Sir John, to the City of Cape Town during the Herschel Centenary celebrations in 1934.
The obelisk was made in England of Craighleith stone and arrived at the Cape in 1841. On 15 February 1841 the obelisk was erected on top of Herschel's cylinder. The inscription on the obelisk was engraved in 1905 and were designed and supplied by three sons of Sir John and a son of Maclear and it reads:
'Here stood from MDCCCXXXIV to MDCCCXXXVIII the reflecting telescope of Sir John F.W. Herschel, Baronet, who during a residence of four years in this colony contributed largely by his benevolent exertions to the cause of education and humanity as by his eminent talents to the discovery of scientific truth.
The site is a provincial heritage site, proclaimed in 1936 in terms of Government Notice 529 dated published in the Government Gazette dated 6 April 1936.
9. The Grand Parade, the Golden Acre and the Old Mutual building, corner of Heerengracht and Strand Street, Cape Town
The Parade is closely associated with the Castle of Good Hope. Most of the garrison at the Cape were billeted in the Castle and a parade ground was essential for their proper training. The Parade was proclaimed as a national monument in 1962. It is now a provincial heritage site.
The Golden Acre contains the ruins of Wagenaers' Reservoir, proclaimed a national monument in
The commemorative memorial or monument dedicated to Abbé de la Caille on the groundfloor of the Old MutuaI Building is also protected in terms of section 36 of the National Heritage Resources Act, 1999.
10. The Heerenlogement Cave, Clanwilliam District
Although a shelter for millennia for the indigenous Khoisan, some of the pioneer travellers from the Cape to Namaqualand and further north frequented the Heerenlogement Cave ever since the first expedition left the Cape in 1655. These included Pieter van Meerboff (1661), Oloff Bergh (1682), Simon van der Stel (1685-1686), Slotsbo (1712), Rhenius (1721), Thunberg (1774) and Swellengrebel (1777).
Swellengrebel described the area: 'These mountains bear the name of Heerenlogement because there are several cavities amongst the rocks piled against one another, including two that are like very large rooms; at the end of one of these there is a natural stage as in a theatre; both of them resemble amphitheatres.
Here several trees grow out of the rock without any earth round them.
During the 19th century the cave was visited by more well-known travelers all of whom added their names to those of their predecessors: The Rev. Barnabas Shaw (1816), Capt James Alexander, the Rev James Tindall (1839), James Backhouse (1840) and Andrew Geddes Bain (1854), amongst others.
It is therefore not surprising that Maclear chose the Heerenlogement Cave as a site to set up the Zenith Sector in 1842 when he extended the Arc of Meridian northwards.
11. The Company Gardens, Cape Town

Land ownership:
1.1 Maclear's Beacon falls within the land now managed by the SA National Parks as part of the Table Mountain National Park
1.2 The site on which the Eastern Terminal is situated is privately owned.
1.3 The site on which the Northern Terminal is situated is privately owned.
1.4 The site on which the Western Terminal is situated is privately owned.
1.5 The South African Astronomical Observatory is a facility of the National Research Foundation of the Department of Science and Technology of the Republic of South Africa owns the Royal Observatory site in Cape Town.
1.6 The Time-ball Tower in the V&A Waterfront in Cape Town is owned by Victoria&Albert Waterfront Properties (Pty) Ltd.
1.7 The Herschel Monument/Obelisk is situated in the grounds of The Grove Primary School in Claremont, Cape Town, is owned by the Western Cape Provincial Government's Education Department.
1.8 The Golden Acre is owned by Sanlam Properties (Pty) Ltd and the Old Mutual Building in Strand Street is owned by Old Mutual Properties (Pty) Ltd.
1.9 The Heerenlogement Cave is privately owned.

Management Structure: Should the site be placed on the Tentative List of World Heritage Sites in South Africa, an integrated management plan in collaboration with the owners and key stakeholders, will need to be developed based on the requirements of the Operational Guidelines and prior to the formal nomination of the site.
In 2006 Heritage Western Cape, the provincial heritage resource authority of the Western Cape Province, decided to support the proposed nomination of the Cape Arc of Meridian and related sites on the South African Tentative List

Budgetary matters: The proposed management plan will also need to address the financial matters related to the management of the proposed sites.

Site readiness: A nomination dossier has not yet been prepared. However, given the decision of the 29th Session of the World Heritage Committee, held in Durban, South Africa, as a member state, should consider implementing the decisions of the World Heritage Committee and should include this nomination on the South African Tentative List of World Heritage.

Justification de la Valeur Universelle Exceptionelle

The Cape Arc of Meridian and the related beacons, terminals, sites and structures should be included in a transcontinental serial nomination with the existing inscription of the Struve Arc in 2004 on the World Heritage List based on the following criteria:

Criterion (ii): The first accurate measuring of a long segment of a meridian in the southern hemisphere, helping in the establishment of the exact size and shape of the earth exhibits an important step in the development of earth sciences. It is also an extraordinary example for interchange among scientists from different countries. It is al the same time an example of the collaboration between monarchs, heads of state and powers of sometimes opposing countries and territories for a scientific cause.

Criterion (iv): The Cape Arc of Meridian is undoubtedly an outstanding example of a technological ensemble presenting the triangulation points of the measuring of the arc of the meridian, being the non-movable and non-tangible part of the measuring technology.

Criterion (vi): The measuring of the Cape Arc of Meridian and the Struve Arc and the results are directly associated with men and women wondering about their world, its shape and size. It is linked with Sir Isaac Newton's theory that the world is not an exact sphere and the opposing viewpoints of the time and how these theories were proven or refuted by the data that was collected.

Déclarations d’authenticité et/ou d’intégrité

Together with the Struve Arc (a chain of survey triangulations stretching from Hammersfest in Norway to the Black Sea, through 10 countries and over 2,820km in the northern hemisphere), The Cape Arc of Meridian confirmed the measurements taken to determine the exact size and shape of our planet. The Arc of Meridian, surveyed by the Abbé Nicholas-Louis de Lacaille in 1751-1753 and Thomas Maclear from 1838-1848 represented the first accurate measuring of a long segment (137km or 1¼º) of a meridian in the southern hemisphere. It marked an important slep in the development of earth sciences and geodetic mapping, not only of South Africa, but of the African continent. At the same time significant contributions to astronomy was made by the persons associated with the Arc of Meridian.

The measurements of the Arc of Meridian and the related other scientific observations of the scientists are still credible and are the scientific bases of not only geodetic/trigonometric measurements of the earth, but also of the southern constellations and stars.

The terminals, beacons, sites and structures related to the Cape Arc of Meridian represent a complete picture that conveys the significance of the site. The beacons, sites and structures are in good condition and are still in use and are maintained by the various owners and authorities.

Comparaison avec d’autres biens similaires

Maritime Greenwich, London, United Kingdom: Greenwich, on the south bank of the River Thames, is famous for its naval and military connections and its green spaces. Fronting the Thames is the famous Greenwich Park, in which the Royal Greenwich Observatory, the National Maritime Museum and the Royal Naval College are found. In 1433 Humphrey Plantagenet, the duke of Gloucester, enclosed Greenwich Park and built a watchtower on the north-facing hill above the Thames.

The ensemble of buildings at Greenwich and the park in which they are set, symbolize English artistic and scientific endeavour in the 17th and 18th centuries. The Queen's House, designed by Inigo Jones and the first Palladian-style building in England, was commissioned as a residence for Anne of Denmark. It was completed in the 1630s for Queen Henrietta Maria, consort of Charles I. The house was later converted into a school (1806), and colonnades to the original building joined two new wings. Since 1937 Queen's House has been part of the National Maritime Museum. Christopher Wren designed the complex that was until recently the Royal Naval College.

The Royal Greenwich Observatory, also designed by Christopher Wren, stands on the bill above these buildings. The observatory, with its high-vaulted Octagon Room, was erected in the I7th century. By 1957 its official functions had been transferred elsewhere, and the site was subsequently made a museum. The prime meridian (0°) mark. which since 1884 bas been the world standard for reckoning longitude, is still on display, as is a collection of early astronomical instruments. The observatory was extensively restored by 1993. The park, laid out on the basis of an original design by André le Nôtre, contains the Old Royal Observatory, the work of Wren and the scientist Robert Hooke.

The Greenwich Meridian 15 the imaginary line that used to indicate 0° longitude that passes through Greenwich and terminates at the North and South poles. An international conference held in Washington, D.C., in 1884 designated 'the meridian passing through the centre of the transit instrument al the Observatory of Greenwich as the initial meridian for longitude." The observatory (renamed the Royal Greenwich Observatory) was moved to Hailsham, East Sussex, during the 1950s, but the original site continues to serve as the location for 0° longitude. As the prime meridian, the north-south line al Greenwich is used as the reference for all other meridians of longitude, which are numbered east or west of it. The Greenwich meridian also serves as the basis for the world's standard time zone system. The mean solar time at Greenwich is now called Universal Time and was formerly called Greenwich Mean Time. Theoretically, standard time becomes successively one hour earlier at each 15° longitude west of the Greenwich meridian and one hour later at each 15° longitude east.

Maritime Greenwich was inscribe on the World Heritage List on the basis of criteria (i), (ii), (iv) and (vi), considering that the public and private buildings and the Royal Park al Greenwich form an exceptional ensemble that bears witness to human artistic and scientific endeavour of the highest quality, to European architecture at an important stage of its evolution, and to the creation of a landscape that integrates nature and culture in a harmonious whole. This area, which is also known as Maritime Greenwich. was inscribed on UNESCO's World Heritage list in 1997.

The Ancient Observatory, Beijing, China

In the 13th century Kublai Khan founded the first observatory on the site of the current Ancient Observatory in Beijing to reform the then inaccurate calendar used in China. The present Ancient Observatory, known as the Star Observatory, was built in 1442, the 6th Year of Ming Dynasty. The name was shortened to Observatory during the Qing Dynasty, and to Central Star Observatory after the Revolution in 1911. As one of the world's oldest observatories, it has celebrated nearly 500 years of successive astronomical observation, from the Zhengtong period of the Ming Dynasty to the year 1929.

At one time, Muslim scientists staffed the observatory. In 1603 Matteo Ricci (1552-1610), a Jesuit priest, arrived in Beijing from Macao and proceeded to astonish the local citizens and the Chinese emperor by making a series of precise astronomical forecasts. The emperor granted the Jesuits permission to man the Ancient Observatory, which was re-equipped by the Jesuit priests. They remained in charge of the Ancient Observatory until1830.

The Observatory consists of a 10-meter high brick Watching Star Platform and also contains the Purple Hall, Eastern Wing, the Western Wing and the Sun's Shadow Hall. Eight huge bronze astronomical instruments are displayed on top of the terrace. Navigational equipment from the Yuan (Mongol) Dynasty and astronomical instruments, such as armillary spheres and theodolites, from the Ming Dynasty, decorated with dragons, lions and clouds are exhibited in the Observatory. The Celestial Globe, made in 1673 during the Qing Dynasty was designed for measuring the lime and azimuth of the rising and setting of celestial bodies.

The Ancient Observatory is currently being restored and it is reported that it is the Chinese authorities' intention to include it on the Tentative List of World Heritage Sites for China.

The Struve Arc, stretching over 10 countries in Europe

The Struve Arc is a chain of survey triangulations stretching from Hammersfest in Norway to the Black Sea., through 10 countries and over 2,820km. These points of survey, carried out between 1816 and 1855 by the astronomer Friedrich Georg Wilhelm Struve, which represented the first accurate measuring of a long segment of a meridian in the northern hemisphere. This helped establish the exact size and shape of our planet and marked an important step in the development of earth sciences and topographic mapping. It is an extraordinary example of scientific collaboration among scientists from different countries and of collaboration between monarchs for a scientific cause. The original arc consisted of 258 main triangles with 265 main station points. The listed site includes 34 of the original station points, with different markings. i.e. drilled hole in rock, iron cross, cairns, or built obelisks.

The Struve Arc was inscribed on the World Heritage List in 2005 on the basis of the following criteria:

Criterion (ii): The first accurate measuring of a long segment of a meridian, helping in the establishment of the exact size and shape of the world exhibits an important step in the development of earth sciences and the application of technology and knowledge. It is an extraordinary example for interchange among scientists from different countries and at the same time an example for collaboration between different powers for a scientific cause.

Criterion (iv): The Struve Arc are undoubtedly an outstanding example of a technological ensemble presenting the triangulation points of the measuring of the Arc, being the longest non-movable and non-tangible part of measuring technology on the planet.

Criterion (vi): The measuring of the Arc and its results are directly associated with men wondering about his world, its shape and size. It is linked with Sir Isaac Newton's theory that the world is not an exact sphere.

The inscription of the Struve Arc was CONDITIONAL in that the related sites in South Africa are also to be inscribed on the World Heritage List (this conditional inscription was proposed by Argentina). This conditional inscription places an obligation on South Africa as a member state to consider the proposed inscription and to consider adding this site to the Tentative List of South African World Heritage sites.

It is therefore recommended that the South African World Heritage Advisory Committee considers the decision of the 29th Session of the World Heritage Committee to add the Cape Arc of Meridian and the related beacons, terminals, sites and structures to the Tentative List of South African World Heritage sites as a proposed transnational serial nomination (see paragraph 138 of the Operational Guidelines on the basis of criteria (ii), (iv) and (vi).