CHAPTER XIII. 

 THE GREAT ICE AGE. 



SCIENTIFIC superstitions, understanding by this name 

 w_} the reception of hypotheses of prominent men, and using 

 these as fetishes to be worshipped and to be employed in 

 miraculous works, are scarcely less common in our time than 

 superstitions of another kind were in darker ages. One of 

 these which has been dominant for a long time in geology, 

 and has scarcely yet run its course, is that of the Great Ice 

 Age, with its accompaniments of Continental Glaciers and 

 Polar Ice Cap. The cause of this it is not difficult to 

 discern. The covering of till, gravel and travelled boulders 

 which encumbers the surface of the northern hemisphere 

 from the Arctic regions more than half way to the equator, 

 had long been a puzzle to geologists, and this was increased 

 rather than diminished when the doctrine of appeal to recent 

 causes on the principle of uniformity became current. It was 

 seen that it was necessary to invoke the action of ice in some 

 form to account for these deposits, and it was at the same 

 time perceived that there was much evidence to prove that 

 between the warm climate of the early Tertiary and the more 

 subdued mildness of the modern time there had intervened 

 a period of unusual and extreme cold. In this state of 

 affairs attention was attracted to the Alpine glaciers. Their 

 movement, their erosion of surfaces, their heaping up of 

 moraines bearing some resemblance to the widely extended 

 boulder deposits, their former greater extension, as indicated 



