MATTER, LIVING FORCE AND HEAT. 7 



we have been speaking is one of the most important qualities 

 with which matter can be endowed, and, as such, that it 

 would be absurd to suppose that it can be destroyed, or even 

 lessened, without producing the equivalent of attraction 

 through a given distance of which we have been speaking. 

 You will therefore be surprised to hear that until very 

 recently the universal opinion has been that living force 

 could be absolutely and irrevocably destroyed at any one's 

 option. Thus, when a weight falls to the ground, it has 

 been generally supposed that its living force is absolutely 

 annihilated, and that the labour w r hich may have been 

 expended in raising it to the elevation from which it fell has 

 been entirely thrown away and wasted, without the pro- 

 duction of any permanent effect whatever. We might 

 reason, a priori, that such absolute destruction of living 

 force cannot possibly take place, because it is manifestly 

 absurd to suppose that the powers with which God has 

 endowed matter can be destroyed any more than that they 

 can be created by man's agency ; but we are not left with 

 this argument alone, decisive as it must be to every 

 unprejudiced mind. The common experience of every one 

 teaches him that living force is not destroyed by the friction 

 or collision of bodies. We have reason to believe that the 

 manifestations of living force on our globe are, at the 

 present time, as extensive as those which have existed at 

 any time since its creation, or, at any rate, since the 

 deluge —that the winds blow as strongly, and the torrents 

 flow with equal impetuosity now, as at the remote period 

 of 4000 or even 6000 years ago ; and yet we are certain 

 that, through that vast interval of time, the motions of the 

 air and of the water have been incessantly obstructed and 

 hindered by friction. We may conclude, then, with 



