2l6 CARNEGIE INSTITUTION OF WASHINGTON. 



sources of energy has been some time suspected,* and is now being 

 revealed by refined physical research. The extraordinary energies 

 displayed by radio-active substances are doubtless but an initial 

 demonstration of immeasurable energies resident in other forms of 

 matter and in the constitution of the sidereal system and competent 

 for its maintenance for unassignable periods. It does not appear, 

 therefore, in the light of recent revelations in physics or recent dis- 

 coveries in the constitution of the stars and the stellar systems, that 

 there is any sufficient reason for setting narow limits to the life of 

 the sun. It seems more in accord with recent advances in knowl- 

 edge to place the compressional theory of the sun's heat in the cate- 

 gory of the earlier chemical and meteoritic theories as true and 

 contributory, but as only partial and inadequate. 



There seem to be no sufficient grounds, therefore, for hesitating 

 to postulate an ancestral solar system, the center of which was the 

 parent of the present sun. This involves the further quite reason- 

 able assumption that the sidereal system has had a very prolonged 

 history, and that the ancestral sun played its own part in it as the 

 solar system does now. 



* I wrote in 1899, before experimental demon.stration had been reached : 

 " 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 enormous 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 magni- 

 tude. No cautious chemist would probably venture to assert that the compo- 

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

 revolution, position, and be otherwise comparable in kind and proportion 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 energ}'. The Helmholtzian theory takes no cog- 

 nizance 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 j'et 

 probed the bottom of the sources of energy and are able to measure even roughly 

 its sum total ? ' ' (On Lord Kelvin's Address on the Age of the Earth as an Abode 

 Fitted for Life, Science, vol. IX, June 30, and vol. X, July 7, 1899.) 



