THE AGE OF THE EARTH AS AN ABODE FITTED FOR LIFE. 239 



further assumption, by implication, that no other essential factors 

 entered into the problem. Are these assumptions beyond legitimate 

 question? In the first place, without questioning its correctness, is it 

 safe to assume that the Helmholtzian hypothesis of the heat of the 

 sun is a complete theory? Is present knowledge relative to the 

 behavior of matter under such extraordinary conditions as obtain in 

 the interior of the sun sufficiently exhaustive to warrant the assertion 

 that no unrecognized sources of heat reside there? What the internal 

 constitution of the atoms may be is yet an open question. It is not 

 improbable that they are complex organizations and the seats of enor- 

 mous energies. Certainly, no careful chemist would affirm either 

 that the atoms are really elementary or that there may not be locked 

 up in them energies of the first order of magnitude. No cautious 

 chemist would probablj^ venture to assert that the component atome- 

 cules, to use a convenient phrase, may not have energies of rotation, 

 revolution, position, and be otherwise comparable in kind and propor- 

 tion to those of a planetary system. Nor would he probably feel 

 prepared to affirm or deny that the extraordinary conditions which 

 reside in the center of the sun may not set free a portion of this 

 energy. The Helmholtzian theory takes no cognizance of latent and 

 occluded energies, of an atomic or ultra-atomic nature. A ton of ice 

 and a ton of water at a like distance from the center of the system are 

 accounted equivalents, though they differ notably in the total sum of 

 their energies. The familiar latent and chemical energies are, to be 

 sure, negligible quantities compared with the enormous resources that 

 reside in gravitation. But is it quite safe to assume that this is true 

 of the unknown energies wrapped up in the internal constitution of the 

 atoms ? Are we quite sure we have 3^et probed the bottom of the sources 

 of energy and are able to measure even roughly its sum total ? 



There are some things hereabouts in the instruction we receive that 

 puzzle us with our geological limitations: 



1. We are taught that there is a certain critical temperature for 

 ever}" substance, above which it takes the gaseous form and no amount 

 of pressure can reduce it to the liquid or solid state. 



2. We are taught that gases are compressible to an indefinite extent 

 provided their temperatures be above the critical point. 



3. We are told the temperature of the interior of the sun is prob- 

 ably above the critical temperature of any known substance, and hence 

 that all the material of the interior of the sun is probably gaseous. 



4. We are taught that so long as the substances of the sun remain 

 in the gaseous condition the temperature of the sun must rise from 

 increased self -compression. It can not, therefore, fall to the critical 

 temperature of the component substances, and must, therefore, con- 

 tinue in the gaseous state and grow hotter and hotter. 



6. We are taught that gravit}' varies inversely as the square of the 



