52 LIMITS ATsD METHOD OF THE 



degree of precision, confirm the Newtonian axiom, that the 

 acceleration occasioned by the attraction of the earth is 

 identical in bodies the most heterogeneous in composition, 

 viz., water, gold, quartz, granular limestone, and portions 

 of different aerolites. Purely astronomical observations add 

 their testimony to the proofs afforded by the pendulum. 

 The almost identical results found for the mass of Jupiter, 

 from its influence on his own satellites, on Encke's comet of 

 short period, and on the small planets, Vesta, Juno, Ceres, 

 and Pallas, equally teach that, as far as our observations 

 reach, the attraction of gravitation is determined solely by 

 the quantity of matter ( 23 ) . 



Tin's absence of all perception (derived either from obser- 

 vation or from theoretical considerations) of any heteroge- 

 neous qualities of matter, gives to celestial mechanics a high 

 degree of simplicity. The study of the immense regions of 

 space being directed by the laws of motion only, the sidereal 

 portion of the Cosmos draws from the pure and abundant 

 sources of mathematical astronomy, as the terrestrial portion 

 does from those of physics, chemistry, and organic morpho- 

 logy. But the domain of the three last-named sciences 

 embraces phenomena so complex, and, to the present time, 

 so little susceptible of the application of rigorously exact 

 methods, that the physical knowledge of the globe cannot 

 boast of the certainty and simplicity in the exposition of 

 facts and of their mutual connection, which characterise the 

 celestial portion of the Cosmos. This difference may be the 

 true reason why, in the early times of the intellectual culti- 

 vation of the Greeks, the natural philosophy of the Pytha- 

 goreans was directed to the heavenly bodies in space, rather 

 than to the earth and her productions ; and became through 



