312 WRITINGS OF JOSEPH HENRY. [1853 



scarcely any loss and almost inconceivable velocity to the 

 greatest distance. A wave of disturbance starting from the 

 impulse given at the battery will traverse the circumference 

 of the earth in less time than I have been occupied in stating 

 the fact. 



Besides electricity and the principles before mentioned, 

 there are other agents employed between the primary power 

 and the work, namely, the elastic force of steam, of air, and 

 of springs ; also various instruments called machines. But 

 these must not be confounded, as they frequently are, with 

 the sources of power. It is not the engine which is the 

 source of motion of the cars, nor yet the steam, but the re- 

 pulsive energy imparted to the expanding water from the 

 burning fuel. 



A machine is an intermediate instrument to transmit, to 

 modify, and to apply power; and with the exception of the 

 power consumed in wearing away the rubbing parts — (that 

 is, in producing friction,) and the small portion imparted to 

 the air, the amount of power transmitted is just equal to 

 that received. 



The human body is itself an admirably contrived complex 

 machine, furnished with levers, pulleys, cords, valves, and 

 other appliances for the application and modification of the 

 power derived from the food. It is, in fact, a locomotive en- 

 gine, impelled by the same power which under another form 

 gives activity and energy to the iron horse of the railway. 

 In both, the power is derived from combustion of the carbon 

 and hydrogen of the organic matter employed for food or 

 fuel. In both the direction of power is under the influence 

 of an immaterial, thinking, willing principle called the soul. 

 But this must not be confounded, as it frequently is, with 

 the motive-power. The soul of a man no more moves his 

 body than the soul of the engineer moves the locomotive and 

 its attendant train of cars. In both cases the soul is the 

 directing, controlling principle, not the impelling power. 

 Let, for example, a locomotive engine be placed upon the 

 track, with water in the boiler and fire in the grate — in short, 

 with all the potentials of motion, and it will still remain 



