62 ORGANIC FUNCTIONING 



some time in the future — when it may be possible to accelerate 

 the radio-active disintegrations of bound atoms. 



At present man cannot make use of the energy of motion of 

 the molecules of sea water at its natural temperature. But it 

 is conceivable that some marine bacteria can do so. 



20. ON THE FORMS OF ENERGY WHICH IS AVAILABLE 



Energy w^hich is available — that is, which can set up physical 

 changes — exists in many forms : Thus we know — 



The energy of motion, or of state, of material bodies, as, for 

 examples, the mechanical energy of moving bodies or machines 

 such as heat engines ; the mechanical energy of winds and rivers ; 

 the mechanical energy of a raised weight, or a coiled spring, etc. ; 



the energy of heat ; 



chemical energy, such as that manifested in combustions and 

 explosions, etc. ; 



electric energy ; magnetism ; 



radiation. 



2oa. Energy- TRANSFORMATIONS. Whenever any physical 

 change, event, artificial phenomenon, or natural occurrence takes 

 place the available energy of the system which we observe under- 

 goes transformation. Examples are : 



(i) Coal is burned in the furnace of a steam-engine (chemical 

 energy transforms into heat) ; 



{ii) heat (via the generated steam) actuates the engine (the 

 energy of the microscopic molecules of steam transforms into 

 the energy of the macroscopic material bodies (cranks, wheels, 

 etc.) of the engine ; 



(iii) the engine rotates a dynamo and the rotation of the 

 parts of the latter establishes magnetic fields ; conductors move in 

 these fields and electric currents are set up in them (mechanical, 

 transforms into magnetic and electric energies) ; 



(tv) the dynamo sends currents through the motors of a 

 tramcar (electric, transforms into mechanical energy) ; 



{v) the current passes through a glow lamp (electric, trans- 

 forms into radiant (light) energy ; 



(vi) the current charges an accumulator (electric, transforms 

 into chemical energy). 



Solar radiation transforms into the chemical energy of the 

 cellulose of green plants ; 



