De la carte de la France et de la perpendiculaire à la méridienne de Paris, prolongée vers l’Occident (et) l’Orient. by (Cassini, Jacques) - no date 1730s.: 2 parts in one volume. French manuscript on paper.

21 unumbered leaves; 22 unumbered leaves, with two large folding manuscript maps in two colours (580 x 236 mm). Cont. French red morocco binding on five raised and gilt bands. Spine richly gilt in compartments. Front cover with gilt arms of Germain-Louis Chauvelin, marquis de Grosbois. Marbled endpapers. 4to (238 x 183 mm). Spine-ends carefully restored.


Cf. Poggendorff I, 390/391 ; Hockey, Biographical Encyclopedia of Astronomers I, 207 ; DSB III, pp. 104-105 ; Gallois, L'Académie des Sciences et les origines de la carte de Cassini. In: Annales de Géographie, 1909 pp. 289-310. Jacques Cassini (1677-1756), a French astronomer and geodesist who was admitted to the Académie des Sciences in 1694 and began to undertake scientific work on projects which his father was carrying out. Cassini, like his father, was interested in making both astronomical observations and was also interested in accurate surveys. After the Italian trip, Cassini visited Flanders and then England in around 1698. While in England he met Newton, Flamsteed, and Halley and was elected to the Royal Society of London. After returning to France he published the astronomical and geodesic data which he had gathered on his travels. In 1700 Cassini's father undertook a project to measure the meridian from Paris to Perpignan, which is 13 km west of the Mediterranean coast. Cassini assisted his father on this project and they obtained results which wrongly suggested that the Earth was elongated at the poles. In 1713 he proposed a new method for determining longitude by means of the eclipses of the stars and planets by the moon. Applying this method, and using data from the 1700 Paris to Perpignan survey, he claimed to have proved that the degrees of the terrestrial meridian grow smaller from the equator towards the pole. It was unfortunate that Cassini resolutely stuck to this position throughout his life, refusing to acknowledge the flattening despite the scientific evidence which was put forward. Whether this was due to a false sense of patriotism, believing that he was supporting the French view against the English view which was a consequence of Newton's gravitational theory (which Cassini never accepted), or whether it was through a false sense of family loyalty supporting his father's views, we shall never know. Perhaps indeed both may have contributed without Cassini being fully aware that they were affecting his scientific judgement, or perhaps he was so convinced that the results of the 1700 survey were correct that he could never accept the contrary. The real problem with the data from the survey was, as pointed out in 1733 by Giovanni Poleni, that both the elongation proposed by Cassini or the flattening proposed by others, fell within the experimental error of the instruments used. His scientific role was one of major importance, playing a major role in the Académie des Sciences and taking over as head of the Paris Observatory from his father in 1709. Cassini continued both his astronomical and surveying work. In 1718 he undertook the measurement of the Paris meridian north to Dunkerque and in 1722 he published the results, which again supported his incorrect theory of elongation at the poles, in "De la grandeur et de la figure de la terre". This important treatise surveyed the results which had been obtained on measuring the earth over the preceding fifty years. However, those like Maupertuis who believed that the earth was flattened at the poles argued ever more strongly against Cassini's theory and, in an attempt to gain further evidence to support his case, Cassini organised another project in 1733, this time to measure the perpendicular to the meridian from Saint-Malo to Strasbourg. As he had accompanied his father when he was a young man, on this measuring project Cassini had the assistance of his own son César-François Cassini de Thury. The data they collected during the years 1733-34 seemed to support the elongation theory but this only encouraged those members of the Académie such as Maupertuis who supported the Newtonian view, to organise further scientific expeditions in an attempt to settle the argument in their favour. By 1738 the geodesic measurements carried out in Peru by Bouguer and La Condamine in 1735 and in Lapland by Maupertuis in 1736 to measure the length of a meridian degree had produced very strong evidence for the flattening at the poles. Although Cassini never deviated from his belief, he began to scale back his scientific work from 1740. - "Let us end by stressing that Cassini made an extremely important contribution to the major scientific debates of his time. Although he supported an incorrect hypothesis regarding the shape of the Earth, nevertheless his contribution is extremely important. It is in the nature of scientific progress that hypotheses get put forward and tested. We should in no way consider Cassini's contribution any the less important because he was on the wrong side in the debate" (J. J. O'Conor and E. F. Robertson: MacTutor History of Mathematics archive (www.history.mcs.st-andrews.ac.uk/index.html).


- Germain-Louis Chauvelin (1685-1762), marquis de Grosbois, was a French politician, serving as 'garde des sceaux' (seal keeper) and Secretary of State for Foreign Affairs under Louis XV. In 1727 Chauvelin was put in charge of the department related to publishing, printing business and censorship and given the presidency of the seal. The seal right also gave him access to major revenue streams. Barbier called him "prodigiously rich". His impressive library was sold in Paris in 1762 (Blogie, Répertoire des Catalogues II, 1762 VII, 1-28). Our manuscript is listed in the catalogue under no. 2365. The manuscript is teeming with details and anecdotes: We follow Cassini and his men (the astronomer Jean-Dominique Maraldi (1709-1788), the cartographer l'abbé Jean Delagrive (1689-1757), the clock and instrument maker Julien Le Roy (1686-1759) and two of his sons step by step through the villages and towns of France, sometimes faced with major problems to carry out their surveys. Comprising 86 pages, written on thick laid paper in a neat and legible calligraphic hand and adorned with two large manuscript maps accompanying the two parts of the manuscript. The printed version of both texts lectured and published in 1734 at the Académie de Sciences with slight variants and only one of the two maps the one joining Paris to the sea, the other map unpublished (?). One map with short tear in one fold. One of presumedly four existing manuscript copies, of which three in French public institutional holdings dedicated to the king and other important representatives of the French government. A fine and excellently preserved scientific manuscript in a very decorative contemporary French red morocco armorial binding.