64 THE BEGINNINGS OF LIFE. 



heat, the motion in mass, or molar motion, of one body 

 expends itself as the body is arrested in producing 

 an equivalent molecular motion, or motion of the par- 

 ticles, in its own substance and in those of the body 

 by which it has been arrested. But here there is a 

 simple transference of the motion of the mass into the 

 more diffuse motion of the particles of the masses. 

 The motion ceases to exist in the mass as what we 

 ordinarily call motion, though it persists for a time in 

 the atoms or molecules of the masses, and manifests 

 itself in the form of heat. And, similarly, when the 

 expansive motions of the particles of bodies are checked 

 (and mechanical work is done), the heat diminishes in 

 quantity in proportion as a motion of the resisting mass 

 is produced. When heat gives rise to electricity in a 

 thermo-electric pile, a certain quantity of the incident 

 heat ceases to exist as heat. By acting upon the related 

 metals, it has been able to bring about certain mole- 

 cular re-arrangements of the particles of these, and 

 owing to this new arrangement, the attributes of the 

 metals or their force- manifestations are altered. The 

 newly-arranged particles cease to manifest heat, though 

 they show an equivalent amount of electrical pro- 

 perties. Now, in these cases, we do not postulate the 

 existence of a peculiar force in the molecules of the 

 bodies by the influence of which the incident physical 



into certain molecular rearrangements of an unstable kind, on the .over- 

 throw of which the stored-up forces are liberated in new forms, is a 

 process that underlies all organic phenomena.' (Loc. cit. p. 29.) 



