VOL. XL.] PHILOSOPHICAL TUANSACTIONS. 120 



and several other young mathematicians, instructed by M. Cassini in this sort 

 of work. 



M. De Lisle has already said, that all these operations performed in France, 

 for the figure and magnitude of the earth, could not serve to determine the 

 earth's figure out of Frnnce, without the assistance of certain hypotheses ; 

 unless the same thing were undertaken and carried on in the other regions of 

 tlie earth, more northern and southern than France. It was on this considera- 

 tion, that the Royal Academy of Sciences took up the resolution of sending some 

 astronomers to make the like observations as near the equator and the poles as 

 possible, which are the places where the difference of the degrees on the meri- 

 dian ought to be the greatest, according to the different hypotheses. 



In the month of April 1735, three mathen)aticians and astronomers of the 

 academy, viz. Messieurs Godin, Bougher, and De la Condamine, set out from 

 France for the province of Quito, the most northern part of Peru in America; 

 to observe, just under the equinoctial line, the magnitude of some degrees of 

 the meridian and equator. 



As to the other mathematicians and astronomers of the same academy, viz. 

 Messieurs de Maupertuis, Camus, Clairaut, and Monnier, who were sent to 

 the north, they departed from France in April 1730, with Mr. Celsius, pro- 

 fessor of astronomy at Upsal, who accompanied them to Sweden, as far as the 

 bottom of the gulph of Bothnia, where they might measure about a degree on 

 the meridian at its crossing the polar circle. But as they had not finished their 

 operations, it is not yet known whether the magnitude of the degree measured 

 by them, favours the opinion of M. Cassini, or that of Sir Isaac Newton. All 

 we know is, that they have found the length of the simple pendulum favourable 

 to the latter, that is, longer under the polar circle than farther south. De la 

 Croyere had already found the same thing : for being at Archangel in 1728, he 

 there observed, in the most exact manner he possibly could, the length of the 

 simple pendulum, which he found to be -^ parts of a line longer than at Paris. 



We are likewise informed by the other astronomers gone to Peru, that in 

 their way towards the equator, being at St. Domingo, in the latitude of 18° 

 37', they there found the pendulum swinging seconds, to be about 2 lines 

 shorter than at Paris. Thus, all we as yet know from those gentlemen, on the 

 expeditions to the north and the line, confirms the opinion of Sir Isaac Newton 

 and his adherents : and yet M. Mairan pretends, that this shortening of the 

 pendulum towards the equator, is in one sense entirely independent of the 

 earth's figure. 



Thus it appears from the foregoing account, that the question concerning the 

 earth's figure is not yet at an end. Nay, it is not impossible, that after finish- 



VOL. VIIJ. S 



