THE NEBULAR HYPOTHESIS 193 



to contain any desired percentage of radium, or radio- 

 active materials. It might, indeed, dispose of the quanti- 

 tative question, but it would still leave hanging all the 

 aforementioned qualitative difficulties untouched. Pro- 

 fessor W. B. Wright, of the Geological Survey of Ireland, 

 summing up a luminous chapter on the theories as to the 

 causes of ice ages (The Quaternary Ice Age, p. 451), 

 says: 



It must be admitted that, among the theories that have been 

 brought forward to account for the phenomena of the Ice Age, 

 there is not a single one which meets the facts of the case in such 

 a manner as to inspire confidence. An almost fatal objection to 

 Croll's theory is the date it assigns to the end of the Ice Age, 

 which it places some 80,000 years back. If as Doctor Geer seems 

 to have clearly established the ice margin retreated north past 

 Stockholm only about 9,000 years ago, this practically excludes 

 any possibility of a connection between glaciation and changes 

 in the eccentricity of the earth's orbit. 



And listen to this from Dr. Chamberlin, the world- 

 renowned geologist (Origin of the Earth, p. 4) : 



But this theory of a simple decline from a fiery origin to a 

 frigid end, from a thick blanket of warm air to a thin sheet of 

 cold nitrogen, consonant with the current cosmogony as it was, 

 logical under the premises postulated, pessimistically attractive in 

 its gruesome forecast, already in possession of the stage, with a 

 good prospect of holding it this theory of a stupendous descen- 

 sus none the less encountered some ugly facts as inquiry went 

 on. It seemed to accord well enough with an ice age, if the ice 

 age came only in the later stages of the earth's history, but it was 

 ill suited to explain an ice age in the earlier geologic eras. Un- 

 fortunately for it, there began to appear signs of ice ages far back 

 in time, and, besides, some of these had their seats much nearer 

 the equator and, in other respects, were even stranger than the 

 latest great glaciation. The evidence of these earlier and stranger 

 glaciations was at first quite naturally received with incredulity, 

 but the proof grew steadily stronger with every new test, and the 

 range of the evidence was found wider and clearer as exploration 

 advanced. While all this should have weakened, and did weaken, 

 the fundamental concept of great warmth and a rich atmosphere 

 in the earlier ages, while it should have roused skepticism as to 

 the verity of the cosmogony on which it was based, and perhaps 

 did so, still the old thermal concept and the old cosmogony con- 

 tinued to hamper all attempts at a radical revision of glacial 

 theories. 



