Z'Z SPECIAL RESULTS OF OBSERVATION IN THE DOMAIN 



tioii shews itself the most comprehensive and the most rich 

 in cosmical promise. It is indeed true, notwithstanding 

 the brilliant progress made in modern times in Stoechiornetry 

 (calculation of chemical elements and of the ratios of volume 

 in compound gases), we are not yet able to reduce all 

 theories of substances to a mathematical explanation. Em- 

 pirical laws have been discovered, and in following the 

 widely extended views of the atomic or of the corpuscular 

 philosophy, many things have been rendered more accessible 

 to mathematical treatment ; but from the boundless hetero- 

 geneity of matter, and the multifarious conditions of aggre- 

 gation of what are called the particles of mass, the demon- 

 strations of these empirical laws can as yet by no means be 

 derived from the theory of " contact attraction," with the 

 same certainty as is effected by the establishment of 

 Kepler's three great laws on the basis of the theory of 

 " mass attraction" or gravitation. 



Yet, after Newton had recognised all the motions of the 

 heavenly bodies as consequences of one single force, he did 

 not, with Kant, regard gravitation itself as an essential pro- 

 perty of matter, ( 40 ) but as either derived from a higher 

 force still unknown to him, or as the result of a "revolving 

 of the Ether which fills all space, and is more rare in the 

 intervals between the particles of mass, and increases in 

 density outwards." The latter view is developed in detail 

 in a letter to Robert Boyle, ( 41 ) dated 28th February, 1678, 

 which ends with the words, " I seek in the Ether the cause 

 of gravitation." Eight years later, as may be seen from a 

 letter to Halley, Newton gave up this hypothesis of denser 

 and rarer Ether altogether. ( 42 ) It is a striking circumstance 

 that, in 1717, nine years before his death, in the extremely 



