Celebrated Travels and Travellers Vol 2 First Part chapter I - Astronomers and Cartographers part 1

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Section 1 of Celebrated Travels and Travellers, Volume 2 This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit librivox.org. Recording by Abayi in January 2014 Celebrated Travels and Travellers, Volume 2 Great Navigators of the 18th Century. Bye Jules Verne. First part, chapter one, part one. Astronomers and Cartographers. Cassini, Picard and Lahire, The Ark of the Meridian and the Map of France, G de Lille and Donville, The Shape of the Earth, Montperteuil in Lapland, Condamine at the Equator.

Before we enter upon a recital of the great expeditions of the eighteenth century, we shall do well to chronicle the immense progress made during that period by the sciences. They rectified a crowd of prejudices and established a solid basis for the labors of astronomers and geographers. If we refer them solely to the matter before us, they radically modified cartography and ensured for navigation a security hitherto unknown.

Although Galileo had observed the eclipses of Jupiter's satellites as early as 1610, his important discovery had been rendered useless by the indifference of governments, the inadequacy of instruments and the mistakes committed by his followers. In 1660, Jean-Dominique Cassini published his Tables of the Satellites of Jupiter, which induced Colbert to send for him in the following year, and which obtained for him the superintendence of the Paris Observatory. In the month of July 1671, Philippe de Lahire went to Uraniborg in the island of Huen to take observations for the situation of Tichobrah's observatory. In that spot, he calculated with the assistance of Cassini's tables, and with an exactitude never before obtained, the difference between the longitudes of Paris and Uraniborg. The Academy of Sciences sent the astronomer Jean Richter the same year to Cayenne to study the parallaxes of the sun and moon, and to determine the distance of Mars and Venus from the Earth. This voyage, which was entirely successful, was attended with unforeseen consequences, and resulted in inquiries shortly after entered in question as to the shape of the Earth. Richter noticed that the pendulum lost 2 minutes 28 seconds at Cayenne, which proved that the momentum was less at this place than at Paris. From this fact, Newton and Huygens deduced the flatness of the globe at the poles. Shortly afterwards, however, the computation of a terrestrial degree given by Abbé Picard and the determination of the meridional arc arrived at by the Cassini's father and son, led scientific men to an entirely different result and induced them to consider the Earth an elliptical figure, elongated towards the polar regions. Passionate discussions arose from this decision, and in them originated immense undertakings from which Astronomical and Mathematical Geography profited. Picard undertook to estimate the space contained between the parallels of Amiens and Malvoisin, which comprises a degree and a third. The Academy, however, decided that a more exact result could be obtained by the calculation of a greater distance and determined to portion out the entire length of France from north to south in degrees. For this purpose, they selected the Meridian line which passes the Paris Observatory. This gigantic trigonometrical undertaking was commenced twenty years before the end of the seventeenth century, was interrupted and re-commenced, and finally finished towards 1720

At the same time, Louis XIV, urged by Colbert, gave orders for the preparation of a map of France. Men of science undertook voyages from 1679 to 1682, and by astronomical observations found the position of the coasts on the ocean and Mediterranean. But even these undertakings, because computation of the Meridional Arc, the calculations which determined the latitude and longitude of certain large cities in France, and a map which gave the environs of Paris in detail with geometrical exactitude, were still insufficient data for a map of France. As in the measurement of the Meridional Arc, the only course to adopt was to cover the whole extent of the country with a network of triangles. Such was the basis of the large map of France, which justly bears the name of Cassini. The result of the early observations of Cassini and Lair, was to restrict France within much narrower limits than had hitherto been assigned to her. Despros Cooley, in his History of Voyages, says, quote, they deprived her, France, of several degrees of longitude in the length of the western coast from Brittany to the Bay of Biscay, and in the same way retrenched about half a degree from Languedoc and La Provence. End quote. These alterations gave rise to a bone maw. Louis XIV, in complimenting the academicians upon their return, remarked, I am sorry to see, gentlemen, that your journey has cost me a good part of my kingdom.

So far, however, Cartographers had ignored the corrections made by Astronomers. In the middle of the 17th century, Peresque and Cassendi had corrected upon the maps of the Mediterranean a difference of 500 miles of distance between Marseille and Alexandria. The photographer, Jean-Matthieu de Chazelle, who had assisted Cassini in his labors, was sent to the Levant to draw up a coast chart for the Mediterranean. It was sufficiently clear, say the Memoirs of the Academy of Sciences, that the maps unduly extended the continents of Europe, Africa and America, and narrowed the Pacific Ocean between Asia and Europe. These errors had caused singular mistakes. During Monsieur de Chaumont's voyage, when he went as Louis XIV's ambassador to Siam, the pilots, trusting to their charts, were mistaken in their calculations, and both in going and in returning went a good deal further than they imagined. In proceeding from the Cape of Good Hope to the island of Java, they imagined themselves a long way from the Strait of Sunda, when in reality there were more than sixty leagues beyond it. And they were forced to put back for two days with a favorable wind to enter it. In the same way, upon their return voyage from the Cape of Good Hope to France, they found themselves at the island of Flores, the most western of the Azores, when they conceived themselves to be at least a hundred and fifty leagues eastward of it. They were obliged to navigate for twelve days in an easterly direction in order to reach the French coast. As we have already said, the corrections made in the map of France were considerable. It was recognized that Perpignan and Colliure more especially were far more to the east than had been supposed. To gain a fair idea of the alteration, one has only to glance at the map of France published in the first part of the seventh volume of the Memoirs of the Academy of Sciences. All the astronomical observations to which we have called attention are noted in it, and the original outline of the map published by Sanson in 1679 makes the modification apparent.