EXTERNAL APPEARANCE OF GLACIERS. 311 
terminal moraines, their original size, their rough 
surfaces, and their angular form. Whenever, 
therefore, a glacier melts, it is evident that the 
lower materials will be found covered by the 
angular surface-materials now brought into im- 
mediate contact with the former in consequence 
of the disappearance of the intervening ice. The 
most careful observations and surveys have shown 
this everywhere to be the case ; wherever a large 
tract of glacier has disappeared, the moraines, 
with their large angular boulders, are found rest- 
ing upon this bottom layer of rounded materials, 
scattered through a paste of mud and sand. 
We shall see hereafter how far we can follow 
these traces, and what they tell us of the past 
history of glaciers, and of the changes the cli- 
mates of our globe have undergone. 
THE END. 
Cambridge : Stereotyped and Printed by Welch, Bigelow, & Co. 
