454 On the Conservation of Force. [1857. 



thermo-voltaic current, and appears in another ; or when it 

 enlarges or changes the state of bodies ; or what would happen, 

 if the heat being presented, such changes were purposely op- 

 posed. We have a right to ask these questions, but not to 

 ignore or deny the conservation of force ; and one of the high- 

 est uses of the principle is to suggest such inquiries. Expli- 

 cations of similar points are continually produced, and will be 

 most abundant from the hands of those who, not desiring to 

 ease their labour by forgetting the principle, are ready to admit 

 it either tacitly, or better still, effectively, being then continu- 

 ally guided by it. Such philosophers believe that heat must do 

 its equivalent of work ; that if in doing work it seem to disap- 

 pear, it is still producing its equivalent effect, though often in 

 a manner partially or totally unknown ; and that if it give rise 

 to another form of force (as we imperfectly express it), that force 

 is equivalent in power to the heat which has disappeared. 



What is called chemical attraction^ affords equally instruct- 

 ive and suggestive considerations in relation to the principle 

 of the conservation offeree. The indestructibility of individual 

 matter is one case, and a most important one, of the conserva- 

 tion of chemical force. A molecule has been endowed with 

 powers which give rise in it to various qualities, and these never 

 change, either in their nature or amount. A particle of oxygen 

 is ever a particle of oxygen nothing can in the least wear it. 

 If it enters into combination and disappears as oxygen, if it 

 pass through a thousand combinations, animal, vegetable, mi- 

 neral, if it lie hid for a thousand years and then be evolved, 

 it is oxygen with its first qualities, neither more nor less. It 

 has all its original force, and only that ; the amount of force 

 which it disengaged when hiding itself, has again to be em- 

 ployed in a reverse direction when it is set at liberty ; and if, 

 hereafter, we should decompose oxygen, and find it com- 

 pounded of other particles, we should only increase the strength 

 of the proof of the conservation of force, for we should have a 

 right to say of these particles, long as they have been hidden, 

 all that we could say of the oxygen itself. 



Again, the body of facts included in the theory of definite 

 proportions, witnesses to the truth of the conservation of force ; 

 and though we know little of the cause of the change of pro- 

 perties of the acting and produced bodies, or how the forces of 



