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thing still remained to be desired, both from the want of precision in some of the elements on which it was founded, and because it was not sufficient, to give a complete idea of the figure and dimensions of the terrestrial globe. To calculate the length of the degree, Picard had employed thirteen triangles, in a space of thirty two leagues. Now some sensible errours might have crept into the trigonometrical resolutions of so many triangles: and on the other hand the best instruments then known could not give the value of the corresponding celestial arc within four seconds, which four seconds would amount to near seventy toises on the Earth. Lastly, a single degree could not make known, whether the Earth be spherical, or deviate from this figure.
These considerations being laid before the french government, always favourably inclined toward the sciences, it issued orders, not only that Picard's measure should be verified, but that the meridian line should be continued from it to Dunkirk in the north, and to Colioure in the south; which includes a space of about eight degrees. The northern part was entrusted to la Hire; and the southern to Dominic Cassini, who was afterward assisted by his son James. From these operations, begun in 1683 and finished in 1701, it appeared, that the mean length of the degree in France is 57061 toises, about a toise more than Picard assigned it.
The mathematicians employed on these measures, persuaded by the experiment of the shortening of the pendulum at Cayenne, and by the theory of
Huygens and Newton, that the Earth was a spheroid flattened toward the poles; but misled by a false application of geometry, which led them to imagine, that in such a spheroid the degrees of the Earth must diminish in length in proceeding from south to north; were not perhaps sufficiently on their guard against the sources of illusion, to which this prejudice might give rise. Whether from this cause, or from the want of accuracy in their instruments, or from some negligences almost inevitable in so long a series of observations, they found, that the degrees did in fact diminish from south to north: and this result they hastened to publish with the more confidence, as they imagined thereby they confirmed the flattening of the Earth, which was considered as highly probable.
The question appeared to be completely resolved, and philosophers remained for some years secure in the conviction, that the observations agreed with the theory, at least as to the general consequence. But at length some geometricians interrupted this tranquillity. They demonstrated, that this pretended agreement of observation with theory was founded on a geometrical parallogism; and that, in a spheroid flattened toward the poles, the degrees of latitude ought to increase from south to north, and on the contrary diminish in a prolate spheroid.
In fact, it does not require the assistance of a geometrical figure to convince us, that, in an oblate spheroid, the terrestrial meridian being more curved near the equator, than round the pole, the length of
the terrestrial arc of a degree, corresponding to the celestial arc of a degree, must increase in proportion as the curve of the terrestrial meridian diminishes, or in proportion as it approaches the pole. In a prolate spheroid the contrary must take place. The truth of this reasoning, so simple and conclusive, could not fail soon to strike every mind. The authors of the new measures then found themselves greatly embarrassed. On the one hand, unable to reject the demonstrations brought against them; and on the other, unwilling to give up observations, which they considered as very certain; they were at length reduced to assert, that the Earth was elongated toward the poles. New measures, taken likewise in France in 1733 and 1736, seemed to confirm the opinion, that the length of the degree diminished from south to north. Thus for about forty years the Earth was considered, in France at least, as a prolate spheroid, in spite of Huygens and Newton.
Still however geometricians were not convinced. From time to time they renewed their protestations against a system, which they could not reconcile with the laws of hydrostatics. They maintained, that, even supposing the observations made in France to be as accurate as possible, the differences between the degrees were too small to be perfectly ascertained; and that well marked and adequate differences could be obtained only by the comparison of degrees measured in places very remote from each other in their meridian distance. The french government listened to objections so well founded: and the count
de Maurepas, then minister of the academy of sciences, sent a company of mathematicians to measure a degree of the meridian in Peru, near the equator, and another to perform a similar operation in Lapland, within the polar circle.
Godin, Bouguer, and la Condamine set out on their voyage for the former purpose in 1735; and the year following Maupertuis, Clairaut, Camus, and le Monnier repaired to Lapland, being joined by Celsius, the celebrated professor of astronomy at Upsal. The former met with impediments and delays of every kind in their operations, and could not return to France, till near seven years had expired; the others found every thing as they could wish; their work was begun and finished in a short time; and they returned to their country, after being absent only fifteen or sixteen months.
Perhaps it would have been proper, to have waited for the return of the academicians from Peru, before an account was given of operations undertaken for the same purpose; as was the opinion of the more moderate and equitable of the party. But Maupertuis, the leader of the northern expedition, a man eager to appear upon the scene, negatived a proposal so contrary to his views. He made it his first business to proclaim every where, in the academy, to the public, and among the great, with whom he had considerable intercourse, the result of an operation, all the glory of which he in some degree appropriated to himself, though he had but a very moderate share in it as a fellow labourer. This result was, that the length of a degree of the meridian, under the polar circle,
amounted to 57438 toises [122365 yards] nearly. On comparing this with the length of the degree in France, it appears incontestible, that the degrees increase in length toward the north, and that consequently the Earth is a spheroid flattened at the poles. It was found likewise, that the axis of revolution of this spheroid, and the diameter of it's equator, are to each other nearly as 177 to 178.
These conclusions were enthusiastically adopted by a numerous party. Maupertuis was extolled, as if he had benefited mankind by discovering a new and extraordinary truth. In certain places he was called by no other name but that of l'applatisseur de la Terre,
the flattener of the Earth.' He had a portrait of himself painted, in which Lapland was the scene, and his hand was placed on the terrestrial globe, as if to compress it into a spheroidal form. Voltaire, who was at that time his friend, wrote four bad verses to be placed under the plate engraved from this painting, which were admired at the time, but have since been deservedly forgotten *.
The partisans of the opinion of the prolate figure of the Earth saw with vexation the progress of a system, which in a moment subverted the whole of
* Ce globe mal connu, qu'il a su mesurer,
De lui plaire et de l'éclairir,
This globe, the form of which was not well known, till he contrived to measure it, becomes the monument of his glory, who was destined to please and enlighten that World, of which he ascertained the figure,'