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 



