AN EARLIER BEGINNING. 203 



That the heat was internal is evinced by many proofs of 

 the continued existence of internal heat. You will recall the 

 facts cited in Talk XVII. You will recall the phenomena of 

 geysers and hot springs (Talk XIV). You will remember that, 

 lavas from volcanoes come up from some heated interior (Talk 

 XV). Your thoughts will again glance over the thousands 

 of square miles of surface covered by lavas which issued 

 through fissures in the Age preceding the present (Talk XVI). 

 You will be vividly impressed with the conviction that in- 

 tense,* fusing heat exists within the earth ; and since all heat 

 tends to waste away, you will conclude that the earth's surface 

 temperature was much higher some millions of years ago than 

 it is at present. The wastage of the earth's heat is proved by 

 actual observation. Science has measured the amount of heat 

 which comes to the earth annually that is, the amount on 

 each square yard and has also measured the amount which 

 escapes annually; and it is thus shown that the wastage ex- 

 ceeds the receipts. The earth is growing cold. This great 

 fact is established by experiment, by observation on the escape 

 of heat from within, and by the records of an ancient higher 

 temperature than now exists at the surface. 



Cooling off! That disclosure puts our minds in a new atti- 

 tude toward the world's history. We have to contemplate the 

 earth as a cooling globe: That points our thoughts backward, 

 along a progress of cooling. That summons us to consider what 

 conditions of the world must have been passed in the progress 

 of cooling. By all the evidence that progressive cooling has 

 been a fact, we are authorized to reason out the events of the 

 cooling history. 



Not the slightest evidence exists that the laws of heat are 

 different under our observation, from the laws which controlled 

 the cooling of the ancient world. We know what they are, 

 and what they were. It is as safe to base backward calcula- 

 tions on them as to base forward calculations on the planetary 

 movements which bring conjunctions and eclipses. We are 

 on the safe ground of reason and science ; we are not soaring 

 on the wing of imagination. We are not calculating events 



