262 DISCUSSION OF THE DESICCATION QUESTION. 



earth's surface, as proved by a long series of facts developed by geological 

 investigation, and of wliich a brief sketch has been given in the preceding 

 pages. Tliis cause is one which has not hitherto found much favor at the 

 hands of geologists, but which, nevertheless, has the support of the very 

 highest authorities in astronomical and mathematical science. Its nature need 

 here be only briefly stated, the present writer not feeling it necessary to do 

 more in support of its claims to acceptance than to give the opinion of one 

 or two of the most eminent living astronomers and physicists in regard to it, 

 with the additional statement that it is as completely in harmony with the 

 conditions required by geological investigation as it is with the demand of 

 exact science. 



What it is, in nature, which has been continuously acting to reduce the 

 temperature of the earth's surface will be made sufficiently apparent by 

 the following quotations taken from recent publications of men occupying the 

 very highest position in the departments of astronomical and physical science. 

 The first of these extracts is from Newcomb, who thus states the case : " But 

 all modern science seems to point to the finite duration of our system in its 

 present form, and to carry us back to the time when neither sun nor planet 

 existed, save as a mass of glowing gas. How far back that was, it cannot 

 tell us with certainty ; it can only say that the period is counted by millions 

 of years, but probably not by hundreds of millions. It also points forward to 

 the time when the sun and stars shall fade away, and nature be enshrouded 

 in darkness and death, unless some power now unseen shall uphold or restore 



her We all know that the sun has been radiating heat into space 



during the whole course of his existence The stars radiate heat as 



well as the sun Thus we have a continuous radiation from all the 



visible bodies of the universe, which must have been going on from the 

 beginning. Until quite recently, it was not known that this radiation in- 

 volved the expenditure of a something necessarily limited in supjily, and, 

 consequently, it was not known but that it might continue forever without 

 any loss of power on the part of the sun and stars. But it is now known that 

 heat cannot be produced except by the expenditure offeree, actual or poten- 

 tial, in some of its forms, and it is also known that the available supply of force 



is necessaril}^ limited Hence, this radiation cannot go on forever imless 



the force expended in producing the heat be returned to the sim in some 

 form. That it is not now so returned we may regard as morally certain."* 



"* I'oi ular .istfoiiomy, liy Sijiion Newcomb. Xcw York, I87S, iip. 501 -.',02. 



