32 TRUE SOURCE OF 



given, which merely takes another form ; in all we 

 have a force and its effect. By means of the fire 

 which heats the boiler of a steam-engine we can 

 produce every kind of motion, and by a certain 

 amount of motion we can produce fire. 



When we rub a piece of sugar briskly on an iron 

 grater, it undergoes, at the surfaces of contact, the 

 same change as if exposed to heat ; and two pieces 

 of ice, when rubbed together, melt at the point of 

 contact. 



Let us remember that the most distinguished 

 authorities in physics consider the phenomena of 

 heat as phenomena of motion, because the very 

 conception of the creatio7i of matter, even though 

 imponderable, is absolutely irreconcilable with its 

 production by mechanical causes, such as friction or 

 motion. 



But, admitting all the influence which electric or 

 magnetic disturbances in the animal body can have 

 on the functions of its organs, still the ultimate 

 cause of all these forces is a change of condition in 

 material particles, which may be expressed by the con- 

 version, within a certain time, of the elements of the 

 food into oxidised products. Such of these elements 

 as do not undergo this process of slow combustion, 

 are given off unburned or incombustible in the ex- 

 crements. 



Now, it is absolutely impossible that a given 

 amount of carbon or hydrogen, whatever different 

 forms they may assume in the progress of the com- 



