FRICTION. 245 



Here, then, we have a force, most extensive 

 and incessant in its operation, which is absolutely 

 essential to the business of this terrestrial world, 

 according to any notion which we can form. 

 The more any one considers its effects, the more 

 he will find how universally dependent he is 

 upon it, in every action of his life ; resting or 

 moving, dealing with objects of art or of nature, 

 with instruments of enjoyment or of action. 



2. Now we have to observe concerning this 

 agent, Friction, that we have no ground for assert- 

 ing it to be a necessary result of other properties 

 of matter, for instance, of their solidity and 

 coherency. Philosophers have not been able to 

 deduce the laws of friction from the other known 

 properties of matter, nor even to explain what 

 we know experimentally of such laws, (which is 

 not much,) without introducing new hypotheses 

 concerning the surfaces of bodies, &c. hypo- 

 theses which are not supplied us by any other set 

 of phenomena. So far as our knowledge goes, 

 friction is a separate property, and may be con- 

 ceived to have been bestowed upon matter for 

 particular purposes. How well it answers the 

 purpose of fitting matter for the uses of the daily 

 life of man, we have already seen. 



We may make suppositions as to the mode in 

 which friction is connected with the texture of 

 bodies ; but little can be gained for philosophy, 

 or for speculation of any kind, by such conjectures 

 respecting unknown connexions. If, on the other 



