88 FRAGMENTS OF SCIENCE. 



not thought it necessary to dwell upon the mighty mechani- 

 cal energy of their act of combination, but, in passing, I 

 would say that the clashing together of 1 lb. of hydrogen 

 and 8 lbs. of oxygen to form 9 lbs. of aqueous vapor, is 

 greater than the clash of a weight of 1,000 tons falling 

 from a height of 20 feet against the earth. Now, in order 

 that the atoms of oxygen and hydrogen should rise by their 

 mutual attractions to the velocity corresponding to this 

 enormous mechanical effect, a certain distance must exist 

 between the particles. It is in rushing over this that the 

 velocity is attained. 



This idea of distance between the attracting atoms is of 

 the highest importance in our conception of the system of 

 the world. For the world may be divided into two kinds 

 of matter ; or rather the matter of the world may be classi- 

 fied under two distinct heads — namely, of atoms and mole- 

 cules which have already rushed together and thus satisfied 

 their mutual attractions, and of atoms and molecules which 

 have not yet rushed together, and whose mutual attractions 

 are, therefore, as yet unsatisfied. Now, as regards motive 

 power, the working of machinery, or the performance of 

 mechanical work generally, by means of the materials of 

 the earth's crust, we are entirely dependent on those atoms 

 and molecules whose attractions are as yet unsatisfied. Those 

 attractions can produce motion, because sufficient distance 

 intervenes between the attracting molecules, and it is this 

 molecular 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 

 motion consequent on their combination has been expended, 

 no further power can be got out of the mutual attraction 

 of oxygen and hydrogen. As dynamic agents they are 

 dead. If we examine the materials of which the earth's 

 crust is composed, Ave find them to consist for the most part 

 of substances whose atoms have already closed in chemical 



