394 FRAGMENTS OP SCIENCE. 



This idea of distance between the attracting atoms is of 

 the highest importance in our conception of the system of 

 the world. For the matter of the world may be classified 

 under two distinct heads: atoms and molecules which have 

 already combined and thus satisfied their mutual attrac- 

 tions, and atoms and molecules which have not yet com- 

 bined, and whose mutual attractions are, therefore, un- 

 satisfied. Now, as regards motive power, we are entirely 

 dependent on atoms and molecules of the latter kind. 

 Their attractions can produce motion, because sufficient 

 distance intervenes between the attracting atoms, and it is 

 this atomic motion that we utilize in our machines. Thus 

 we can get power out of oxygen and hydrogen by the act 

 of their union; but once they are combined, and once the 

 vibratory motion consequent on their combinations has 

 been expended, no further power can be got out of their 

 mutual attraction. As dynamic agents they are dead. 

 The materials of the earth's crust consist for the most part 

 of substances whose atoms have already closed in chemical 

 union whose mutual attractions are satisfied. Granite, 

 for instance, is a widely diffused substance; but granite 

 consists, in great part, of silicon, oxygen, potassium, cal- 

 cium, and aluminum, whose atoms united long ago, and 

 are therefore dead. Limestone is composed of carbon, 

 oxygen, and a metal called calcium, the atoms of which 

 have already closed in chemical union, and are therefore 

 finally at rest. In this way we might go over nearly the 

 whole of the materials of the earth's crust, and satisfy our- 

 selves that though they were sources of power in ages past, 

 and long before any creature appeared on the earth capable 

 of turning their power to account, they are sources of power 

 no longer. And here we might halt for a moment to 

 remark on that tendency, so prevalent in the world, to 

 regard everything as made for human use. Those who 

 entertain this notion, hold, I think, an overweening opin- 

 ion of their own importance in the system of nature. 

 Flowers bloomed before men saw them, and the quantity 

 of power wasted before man could utilize it is all but infi- 

 nite compared with what now remains. We are truly heirs 

 of all the ages; but as honest men it behooves us to learn 

 the extent of our inheritance, and as brave ones not to 

 whimper if it should prove less than we had supposed. 

 The healthy attitude of mind with reference to this sub- 



