8 THE REALITIES OF MODERN SCIENCE 



motion of pushing and pulling. To operate the hand 

 drill requires skill and practice, but to operate the 

 machine requires less skill and the ability to work. 



From this primitive design we can obtain a concept 

 of a machine as a device in which a motion communi- 

 cated to one part results in a different motion of a 

 second part. Now, although this is a correct statement, 

 it is one that is lacking in human interest or significance. 

 Early man devised machines in his struggle against 

 the rigors of the world about him. From our stand- 

 point, as well as from his, we should consider the ma- 

 chine with reference to its effect on mankind. 



It is work to draw the bow back and forth against 

 the friction of the drill and the block. We call the 

 ability to do work " energy" and say that when work 

 is done energy is expended. The machine requires 

 energy from some source, and material upon which to 

 operate. Push and pull, push and pull, is all that it 

 requires, for in its sequence of motions it accomplishes 

 the results of the most skilled craftsman. And this 

 sequence of events is determined once and for all by 

 the inventor of the machine. The needle of the sewing 

 machine rises and falls on the material beneath it 

 whether it be cloth or the hand of the operator. The 

 loaded gun shoots friend and foe alike provided only 

 the energy in its cartridge is released. 



A machine, then, is a device for producing a definite 

 sequence of motions provided the supply of energy 

 necessary to operate it is released. Unless the ma- 

 chine is broken, in which case, of course, it is not a 

 machine at all, man's only control of it is a permissive 

 one, of allowing it to run or not, by controlling its 



