4 



LAWS OF ENERGY 



TABLE I. 

 MECHANICAL EQUIVALENT OF HEAT. 



UNITS. 



To convert to ergs : Calories x 4-2 x 10 7 = ergs. 



From observation it is found : 



(1) That one form of energy may be transformed into any 

 other form. 



(2) That when any quantity of energy in any one form dis- 

 appears, an exactly equal quantity of another form of energy 

 makes its appearance. 



Energy like matter is therefore indestructible (Law I.). 



Every substance possesses a certain amount of energy. This 

 is called its internal or intrinsic energy. Further, every group 

 of substances has associated with it a certain definite amount 

 of energy as long as it remains unchanged. When any change 

 takes place in the group, or in any member of the group, there 

 is usually a corresponding change in its total energy, either an 

 increase, due to the reception of energy from its environment, 

 or a decrease due to an evolution of energy. Put into other 

 words, each of the new substances will have its own charac- 

 teristic intrinsic energy, and the new group will, in general, have 

 a different total energy-content from that of the original group. 



E.g. Cane sugar + O 2 ~^CO 2 +H 2 O + heat energy. 



Corollaries of the First Law. 



The following two deductions are of biological interest : 



1 . The total energy of a system in a given state is for the system 



