132 UNIVERSITY OF MISSOURI BULLETIN 



Even geologists protested only feebly at the disregard of their 

 facts of observation. The physicists and astronomers were 

 inclined to say, when geological facts that did not harmonize 

 with the theory were pointed out to them: "So much the 

 worse for the facts. Our conclusions are based on the solid 

 rock of mathematical demonstration." 



According to the nebular hypothesis, the uniformitarian 

 doctrine could not, as a geological doctrine, be extended be- 

 yond the formation of the first crust — a time when the earth 

 had already been wound up, so to speak, and had already 

 partly run down. According to this hypothesis the geological 

 history of the earth should be one of decreasing temperature 

 and decreasing rainfall — a history of increasing cold and in- 

 creasing aridity. As long as geological observation had ex- 

 tended no further than the discovery of one glacial period, 

 and that one a very recent ajffair, geologists had no sufficient 

 reason to object to the theory. As long, also, as geological, 

 observation failed to identify periods of great aridity extend- 

 ing over large areas of the earth's surface during its early 

 history, they did not find much inconsistency in the theory, 

 though they were continually in an attitude of silent protest, 

 along with the biologists, at the restrictions placed upon them 

 in the matter of time by the advocates of the theory. This, 

 however, I will refer to in another place. 



The gradually increasing body of geological facts ob- 

 tained from the study of widely separated periods of the 

 earth's history has shown that the glacial period of Pleistocene 

 times, or the Glacial Period, as we usually term it, was only 

 the last one; that glacial periods have occurred repeatedly 

 during the past history of the earth; that they are known to 

 have occurred in fact in almost every one of the great time 

 divisions of the earth's history. They are not confined to 

 recent times geologically, to times when the earth has become 

 permanently cold, but are known to have occurred in the 

 earliest known period of the legible geological record. The 



