736 COSMOS. 



The decrease of gravity from the poles to the equator, 

 which even Picard had long denied, was now generally 

 admitted. Newton recognised the polar compression, and the 

 spheroidal form of the earth as a consequence of its rotation ; 

 and he even vetured to determine numerically the amount of 

 this compression, on the assumption of the homogeneous 

 nature of the mass. It remained for the comparative mea- 

 surements of degrees in the eighteenth and nineteenth cen- 

 turies, at the equator, near the north pole, and in the tem- 

 perate zones of both the southern and northern hemispheres, 

 to determine exactly the mean amount of this compression, 

 and by that means to ascertain the true figure of the earth. 

 The existence of this compression announces, as has already 

 been observed in the " Picture of Nature,"* that which may 

 be named the most ancient of all geognostic events, the con- 

 dition of general fluidity of a planet, and its earlier and pro- 

 gressive solidification. 



We began our description of the great epoch of Galileo, 

 Kepler, Newton, and Leibnitz, with the discoveries in the 

 regions of space by means of the newly invented tele- 

 scope, and we now close it with the figure of the earth, as it 

 was then recognised from theoretical conclusions. " Newton 

 was enabled to give an explanation of the system of the 

 universe, because he succeeded in discovering the force,f 

 from whose action the laws of Kepler necessarily result, and 

 which most correspond with these phenomena since these, 

 laws corresponded to and predicted them." The disco- 

 very of such a force, the existence of which Newton has 

 developed in his immortal work, the Principia, (which com- 

 prise the general sciences of nature) was almost simultaneous 

 with the opening of the new paths to greater mathematical 



* Cosmos, p. 154. The dispute regarding priority as to the know- 

 ledge of the earth's compression, in reference to a memoir read by Huy- 

 gens, in!669, before the Paris Academy, was first cleared up by Delambre 

 in his Hist, de I'Astr. mod. t. i. p. lii. and t. ii. p. 558. Richer's return, 

 to Europe occurred indeed in 1673, but his work was not printed until 

 1679 ; and as Huygens left Paris in 1682, lie did not write the Addita- 

 mentum to the Memoir of 1669, the publication of which was very 

 late, until he had already before his eyes the results of liicher's Pen- 

 dulum Experiments, and of Newton's great work, Philosophies 

 ralis Principia Mathematica. 



f Bessel, in ScJmmacher's JaJt .rbuchfur 1843, s. 32. 



