ioo THE MECHANISM OF LIFE 



This number 4;25 has therefore been accepted as representing 

 in calories and kilogramme-metres the transformation of work 

 into heat, and of heat into work. 



Further measurements on the transformations of other 

 forms of energy, chemical energy and electrical energy, have 

 shown that Joule's law of equivalents is general, and that 

 the quantity of mechanical work represented by any form of 

 energy remains undiminished after transformation, whateyer 

 the nature of that transformation. 



Energy presents itself to us under two forms, potential and 

 actual. Potential energy is slumbering energy, energy localized 

 or locked up in the body. In order to transform potential 

 energy into actual energy, there is required the intervention 

 of an additional awakening, stimulating, or exciting energy 

 from without. This stimulating energy may be almost 

 infinitesimal in amount and bears no quantitative relation to 

 the amount of energy transformed. It is the small amount 

 of work required to turn the key which liberates an indeter- 

 minate quantity of potential energy. 



Actual energy, on the other hand, is energy in movement, 

 awake and alert, ready to be transformed into any other form 

 of energy without the intervention of any such external 

 stimulating force. 



The passage of a given quantity o£ energy from the 

 potential into the actual state is effected gradually, and during 

 the time of transformation the sum of the actual and the 

 potential energy remains constant. 



A weight suspended by a cord possesses a quantity of 

 potential energy equal to the product of its weight into the 

 height through which it can fall. This energy is locked up in 

 a certain space, it cannot be transformed without the inter- 

 vention of some external energy to cut the cord. During the 

 falling of the weight, at the middle of its path, half of this 

 ■dumbering energy has become kinetic, and is represented by 

 the vis lira of the weight, while the other half is still 

 potential and is equivalent to the work which the weight will 

 accomplish during the second half of its fall. At any moment 

 the sum of these two energies, the sleeping and the waking 



