Glacier Work. — Scott. 261 
cleus of solid rock." On the island of Rugen in the Baltic, tlio 
drumlins are said to frequently have a nucleus of Chalk rock, 
while sand and gravel is often associated with the boulder-clay/'' 
It is not within the scope of this paper to discuss but briefiy 
the location, or specific character of the existing glacial mater- 
ial, which necessarily has an important relation to the history 
of the topography of the globe; and also in special palaeolithic 
deposits bears directly upon the question of the existence of man 
during former geological periods, f A consideration of further 
important details must therefore be deferred until a future time. 
The results of investigation which is constantly going on in 
the subject of glaciology can scarcely be predicted, for it is re- 
ceiving much attention. Certain it is that the ice-shett has 
greatly modified the original topography, both by its erosive ef- 
fect and by the thousands of square miles of detritus which it 
scattered over different parts of the globe. This powerful agent 
together with subsec^uent ones of a warmer age, has been ever 
sculpturing the world's surface, and the world in its present 
phvsiographic form is simply the result of the conflict between 
the two great opposing forces : construction and destruction. 
Furthermore, the ice age ^:annot be considered as a past 
epoch in the earth's history, since in polar latitudes glaciation is 
now going on at all altitudes ; is also in progress in temperate 
climates at altitudes between 5,000 and 15,000 feet ; and even in 
the torrid zone, at bights over 15,000 feet. As observation has 
shown that retreat of nearly all present glaciers is in progress, 
it is logical to conclude that the ice age is yet passing away, and 
that the earth has yet to reach the maximum temperature of the 
present geological cycle. 
♦Literature on drumlins, T. C. Chamberlin. Geology of Wisconsin, 
Vol. 1. 1883; Ann. Kept. U. S. Oeol. Surv., 1883; R. D. Salisbury, Geol. 
Soc. of Am.. 1891; G. H. Berlin. Am. Geol., Vol. 13, 1894; James Geikie, 
■Great Ice Age. 
■fSee Article by Prof. A. S. Packard. "An afternoon at Chelles and 
the earliest evidences of human industry in France," Pop. Sci. Mo., 
May, 1902. 
