318 FIGURE OF THE EARTH. 



finally at rest. With this view, two delegations, composed chiefly of members 

 of the Academy, and provided with the most delicate instruments for observing 

 then known, were despatched, one towards the equator, tlie other to a high 

 northern latitude, for the purpose of measuring one or more degrees of the 

 meridian, from the comparison of which measurements, if effected with accuracy, 

 might readily be deduced the direction of the terrestrial compression and its 

 value, or the amount of divergence from a spherical form. 



Mauportuis himself, assisted by Clairaut, Le Monnier, Camus, Outhier, and 

 the Swedish astronomer Celsius, undertook the second of the operations re- 

 ferred to, proceeding to Lapland in 173G, as far as the 76° of latitude ; and 

 although it might have seemed that the rigors of the climate would preser^ ob- 

 stacles little less than insuperable, he had the good fortune to terminate his un- 

 dertaking in scai'cely more than two months. The triangulation extended from 

 the mountain of Kittis at the north to the church of Tornea at the south ; the 

 base, of 7.407 toises, was measui'ed upon the frozen river bearing the latter name, 

 under conditions of exactness scarcely to be attained in any other climate ; the 

 quantity of the arc measured was 57' 29", and the resulting value of the de- 

 gree of the meridian equal to 57.438 toises, or 378 more than the degree of 

 Picard, as would be naturally the case on the supposition of the earth's being 

 flattened towards the poles. 



The other commission destined for the equator, and composed of Godin, La 

 Condamine and Bouguer, had sailed a year earlier, or in 1735, and by order of 

 the Spanish government was joined at Quito by D. Jorge Juan and D. Anto- 

 nio de Ulloa, both worthy, from their zeal and intelligence, to co-operate with 

 the French delegation. To recite the hardships to which these distinguished 

 men were subjected during the eight years occupied in their prescribed task, 

 the disappointments which they encountered, the deficiencies to be remedied, 

 the precautions to be taken, and the sagacity and skill of which they made proof, 

 would be beside our present purpose. Suffice it to say, that their measurement 

 of the arc in Peru, notwithstanding the recent progress of practical astronomy, 

 is still considered as a masterly operation in its kind. 



The degree of Peru, of 56.753 toises, compared with that -which Picard had 

 njeasurcd in the north of France, pointed substantially to the same result with that 

 already obtained by the collation of this last with the degree of Lapland ; that 

 is to say, to the polar compression of the terrestrial globe. To what, then, was 

 it attributable that from the examination of the different degrees of the French 

 meridian there resulted a diametrically opposite consequence to the above ? 

 From the fact before hinted at, that the first base measured by Picard labored 

 under a considerable error, compensated, indeed, as regarded the final result by 

 other errors of quite a distinct kind which were committed in the course of the 

 operations, and which by a rare concurrence of circumstances operated in an 

 opposite direction to the preceding. Without distrusting its exactness, Cassini 

 also took that first line for the base of a triangulation much more extensive and 

 important than that of Picard, and hence arose those incidental anomalies 

 Avhicli involved the learned in so much confusion, until the illustrious La Caille 

 divined from what source that incomprehensible difficulty emanated. Tlie base 

 in question having been rectified by successive admeasurements in 1740-1754, 

 and the calculations corrected, the capital discrepancy, which till that date 

 had interfered with the various geodesic results, disappeared. 



In stating that the contradiction disappeared, we would only be understood 

 to say that, after the epoch just referred to, there was a unanimous concur- 

 rence in the fact of the defective sphericity of the earth and the flattening of 

 its poles ; as regards the definite value of this, and the geometric figure to 

 which our globe most nearly approaches, neither did such unanimity then, nor, 



