50 THE MECHANISM OF LIFE 



Now in every transformation three things are involved: 



1. The intensity of the energy (intensity factor). 



2. The quantity of the energy (capacity factor). 



3. The direction of the transformation (the sign). 



These factors may be illustrated as follows: 



In all these cases there is a system in which an energy trans- 

 formation may occur; thus there may be a steam engine and 

 boiler actuating some mechanism, a water reservoir and wheel, 

 etc. Will a transformation occur in the system, and, if so, what 

 will it do ? To be able to predict these occurrences we must be 

 able to specify the conditions under which the system exists. 

 The steam engine will " go " if the pressure of steam in the 

 boiler is considerably greater than that of the atmosphere, and 

 it will continue to go if this pressure is maintained — that is, if 

 new steam is generated as quickly as steam is drawn from the 

 boiler. So, also, with the water mill: the motor will revolve if 

 there is a sufficient head of water, and to keep it revolving the 

 head must be maintained, or the quantity of water in the reser- 

 voir must be very great, or must be renewed as fast as it is 

 depleted. If an electric current flows, there must be some way 

 of raising electric potential, for a difference of this is the reason 

 why the current flows. But the quantity of current is also a 

 factor; thus the voltage of an electric stove might be the same 

 as that of a lamp, but a greater quantity of current would be 

 necessary in the former case (for heavier wires are employed). 

 Finally, the temperature of a steam radiator 1 foot square might 

 be the same as that of a radiator 6 feet square, but the quantity 

 of heat distributed by the latter would be much greater. 



So there must be a difference of intensity if there is to be a 

 transformation. If a hot-water radiator were at the same 

 temperature as that of the room in which it were placed, there 



