138 POPULAR LECTURES AND ADDRESSES. 



pleasure stop, or strike, or push, or pull any single 

 atom of matter, and so moderate its natural course 

 of motion. Endowed ideally with arms and hands 

 and fingers two hands and ten fingers suffice 

 he can do as much for atoms as a pianoforte 

 player can do for the keys of the piano just a 

 little more, he can push or pull each atom in any 

 direction. 



He cannot create or annul energy ; but just as 

 a living animal does, he can store up limited 

 quantities of energy, and reproduce them at will. 

 By operating selectively on individual atoms he 

 can reverse the natural dissipation of energy, can 

 cause one half of a closed jar of air, or of a bar 

 of iron, to become glowing hot and the other 

 ice-cold ; can direct the energy of the moving 

 molecules of a basin of water to throw the water 

 up to a height and leave it there proportionately 

 cooled (i deg. Fahrenheit for 772 ft. of ascent) ; 

 can " sort " the molecules in a solution of salt or 

 in a mixture of two gases, so as to reverse the 

 natural process of diffusion, and produce con- 

 centration of the solution in one portion of the 



