872 THE COKSERVATION OF FORCE. 



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

 admit it, either tacitly, or, better still, effectively, being then 

 continually guided by it. Such philosophers believe that heat 

 must do its equivalent of work ; that if in doing work it 

 seem to disappear, 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 instruc- 

 tive and suggestive considerations in relation to the principle 

 of the conservation of force. The indestructibility of indi- 

 vidual matter is one case, and a most important one, of the 

 conservation of chemical force. A molecule has been en- 

 dowed 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 disap- 

 pears as oxygen if it pass through a thousand combinations, 

 animal, vegetable, mineral if it lie hid for a thousand years 

 and then be evolved, it is oxygen with its first qualities, nei- 

 ther 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 employed in a reverse direction when it 

 is set at liberty ; and if, hereafter, we should decompose oxy- 

 gen, and find it compounded 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 properties of the acting and produced bodies, or how the 

 forces of the former are hid amongst those of the latter, we 



