Chap, hi.] THE TRANSFOEMATIOIT OF FORCES IN BIOLOGY. 459 



calorific movement may be transformed into an electric move- 

 ment, into a luminous movement, into a molecular chemical move- 

 ment, even into sound, as the beautiful experiment of staging 

 flames proves. Eeciprocally, all these movements may be trans- 

 formed into heat, or into each other. We can, then, affirm theo- 

 retically that there are mechanical equivalents for 'electricity, 

 light, sound, molecular movements which are effected in the 

 chemical reactions, and, as the mechanical equivalent of heat is 

 known, it would suffice to transform these diverse movements into 

 a determinate quantity of heat to have their mechanical equiva- 

 lent. This labour has not yet been performed with sufficient 

 precision. However, Father Secchi has found approximately 

 that the amount of electricity which decomposes 106 milli- 

 grammes of water can raise by 1 degree the temperature of 

 38 grammes of the same liquid.^ If then we take as electric 

 the amount of electricity capable of raising 1 kilogramme of 

 water from to 1 degree, we shall see, by a simple proportion, 

 that this quatitity of electricity is that which can decompose 

 2«,789 of water : 



0^106 : 38 : : a; : 1000» : x, whence a; = — = 2^,789. 



38 



Consequently, this quantity of electricity is equivalent to 1 



calory, or to 424 kilogrammetres. 



Similar determinations we can theoretically conceive to be 

 possible with regard to sound and light, but, in spite of several 

 attempts, the mechanical equivalents of sound and light are yet 

 to be determined. 



Chemical combinations also obey the great law of the correlation 

 of physical forces. It is clear that every chemical combination or 

 decombination reduces itself essentially to movements of atoms and 

 moleculeg. In every chemical combination, millions of atoms are 

 precipitated towards each other, clash against each other, till 

 they have reached a state of stable equilibrium. But here the 

 infinite variety of phenomena renders difficult the calculation of 

 1 A. SeccM, L'Uhit4 des Fmces Physiques, p. 328 (2«. Wit. 1874). 



