28 president's address. 



these changes are not more commensurate with the probable 

 internal heat, may well be because of the absence of water. Jf 

 it.be the case that terrestrial volcanic action is largely induced 

 through atmospheric d nudation and oceanic penetration, then 

 the absence of water and of atmosphere from the moon would 

 sufficiently account for her comparative surface stability, and if 

 to the original gravitational heat be added radium blanketing, 

 then, as in the case of the earth, we can readily admit a prolonged 

 condition of internal high temperature, and the absence of any 

 serious amount of disturbance from shrinkage due to secular 

 cooling. 



If the presence of radium is admitted as a factor in the thermal 

 evolution of earth and moon, it is but a natural step to apply the 

 same reasoning to the sun and thereby to open up a vista of time 

 for the entire solar system greatly in excess of anything hitherto 

 considered by physicists to be admissible. 



Cakbon Dioxide and Geological Climate. — For some years 

 past a good deal of attention has been devoted to the question 

 of the influence on climate of possible variations in the com- 

 position of the atmosphere as regards its carbon dioxide and 

 moisture contents, and more especially on tlie competency of 

 such variations to induce the great climatic changes which are 

 involved in the transition from conditions even warmer than 

 those which are now experienced in temperate regions, to a 

 state of glaciation sufficiently severe to partially invade the 

 tropics. ■ I propose to outline the principles underlying this 

 problem and to show in what manner the effect described might 

 be brought about by the specified changes in atmospheric consti- 

 tution. In all that follows regarding the carbon dioxide theory 

 of glaciation, I do not wish to be understood as entirely indorsing 

 all tf>e details given. The hypothesis seems to me a very 

 beautiful and suggestive one, and my desire is to give, as far as I 

 am able, a concise account of its salient features, leaving my 

 hearers to form their own opinions as to its adequacy as a cause 

 of the observed phenomena. Professor Chamberlin has elaborated 

 this hypothesis in a series of extremely valuable papers full of 



