TEANSrORMATION OF PHYSICAL FORCES. 13 



CHAPTER IL 



TrtANSFORMATION OF PHYSICAL FORCES. 



To prove the indestructibility of forces, we must know how to measure 

 them — Units of heat and of mechanical work— Thermo- dynamics — 

 Measure of forces in living beings — Successive phases of the trans- 

 formation of bodies ; successive throwing off of force under this influ- 

 ence — Thermo -dynamics applied to living beings. 



We have just seen that force, in the different states which 

 it presents, may be now latent, or potential, or again in action, 

 in the form of heat, electricity; or mechanical activity. 



To follow this force through all its different transformations, 

 to establish that no portion of it is lost, a means of measuring 

 it under all its forms is necessary. The chemist can prove 

 the indestructibility of matter, by showing, with a balance, 

 that a gramme of matter will preserve its weight through all 

 the changes of condition that can be imposed upon it. Let 

 that matter be weighed in the liquid state, in the solid state, 

 or in the gaseous state, the weight of a gramme will always 

 be found under the most various volumes and aspects. 



A measure is then necessary for the different manifestations 

 of force. Every quantity of heat, of electricity, or of mechani- 

 cal work ought to be compared with a particular unit, as every 

 weight ought to be compared with the unit of weight. 



Unit of heat. The sensations of heat and cold which we 

 experience at the contact of different bodies do not correspond 

 with the quantity of heat which those bodies contain. Ther- 

 mometrical apparatus are not in a condition to give us the 

 measure of the quantities of heat, since different bodies, 

 presenting to our senses and by the thermometer the same 

 temperature, may yield very unequal quantities of heat. But, 

 to warm the same weight of a body to the same number of 

 degrees, the same quantity of heat will always be necessary. 



Now, according to the agreement which has been come to 

 in France and in many other countries, the unit of heat or 



