OF GEOLOGICAL DYNAMICS. 109 



" help us to conceive such a cycle of change as may 

 " restore to the planet the heat supposed to be lost by 

 " radiation into space" And again, at page 213 

 " It is a favourite dogma of some physicists, that 

 " not only the earth, but the sun itself, is con- 

 " tinually losing a portion of its heat, and that, as 

 " there is no known source by which it can be 

 " restored, we can foresee the time when all life 

 " will cease to exist upon this planet ; and, on 

 " the other hand, we can look back to the period 

 " when the heat was so intense as to be incom- 

 " patible with the existence of any organic beings 

 " such as are known to us in the living or fossil 

 " world." 



" When we consider the discoveries recently 

 " made, of the convertibility of one kind of force 

 " into another, and how light, heat, magnetism, 

 " electricity, and chemical affinity are intimately 

 " connected, we may well hesitate before we accept 

 " this theory of the constant diminution from age 

 " to age of a great source of dynamical and vital 

 " power." These statements are directly opposed 

 to the general principle of the dissipation of 



