COHESION OF SOLIDS. 157 



Sir Isaac Newton devoted many years to the 

 investigation of light, and really accomplished 

 much towards an elucidation of its physical pro- 

 perties ; but without ever having inquired into 

 its connexion with heat, or its wonderful agency 

 in the work of the universe. 



The same illustrious author resolved the cohe- 

 sion of solids and the tendency of heavy bodies 

 towards the centre of the earth, into the same 

 law which determines the aggregation of planets, 

 and their revolutions around the sun : but he 

 did not identify the cause of universal attraction 

 with any known agent. In short, he did not 

 distinctly unfold the fundamental principle of 

 action in nature of expansion and contraction, 

 density and lightness, hardness and softness, so- 

 lidity and fluidity, chemical union and decom- 

 position. There is nothing more remarkable in 

 the history of science, than that the phenomena 

 of attraction should have been so far unfolded and 

 generalized, without any definite knowledge of 

 its cause. It would seem that one of the first in- 

 quiries of the philosopher ought to be, what is 

 the agent or cause of force, by which the atoms 

 of matter are held together? and that the most 

 natural answer would be, that which surrounds 

 and fills the spaces between them. 



It can no longer be disguised, that in regard to 

 the cause of cohesion, capillary attraction, arid 

 gravitation, Sir Isaac Newton has expressed him- 

 self with so much ambiguity as to leave his fol- 



