WARREN UPHAM, ESQ., ON CAUSES OF THE ICE AGE. 205 



jMany parts of the borders of the land underlying this ice- 

 sheet are low and almost level, as is known by the flat- 

 topped and horizontally stratified bergs, but some other 

 areas are high and mountainous. Due south of New Zealand 

 the volcanoes Terror and Erebus, between 800 and 900 miles 

 from the pole, rising respectively about 11,000 and 12,000 

 feet above the sea, suggest that portions or the. whole of 

 this circumpolar continent may have been I'ecently raised 

 h-om the ocean to form a land surface, which, on account of 

 its geographic position has become ice-clad. 

 8 What Avere the causes of the accumulation of the ice-sheets 

 of the Glacial period ? Upon their areas warm or at least 

 temperate climates had prevailed during long foregoing 

 geologic ages, and agam at the present time they have 

 mostly mild and temperate conditions. The Pleistocene 

 continental glaciers of North America, Europe, and Pata- 

 gonia, have disappeared ; and the later and principal part 

 of their melting was very rapid, as is known by various 

 features of the contemporaneous glacial and modified drift 

 deposits and by the beaches and deltas of temporary lakes 

 that were formed by the barrier of the receding ice-sheets. 

 Can the conditions and causes be found which first amassed the 

 thick and vastly extended sheets of land-ice, and whose ces- 

 sation suddenly permitted the ice to be quickly melted away? 

 9 Two classes of theories have been presented in answer 

 to these questions. In one class, which we will first con- 

 sider, are the explanations of the climate of the Ice age 

 through astronomic or cosmic causes, comprising all changes 

 in the earth's astronomic relationship to the heat of space 

 and of the sun. The second class embraces terrestrial or 

 geologic causes, as changes of areas of land and sea, of 

 oceanic currents, and altitudes of continents, while otherwise 

 the earth's relations to external sources of heat are supposed 

 to have been practically as now, or not to have entered as 

 important factors in the problem. 



10 It has been suggested that, as the sun and his planets are 

 believed to be moving forward together through space, the 

 Glacial period may mark a portion of the pathway of the 

 solar system where less heat was supplied from the stars 

 than along the earher and later parts of this pathway. To 

 this suggestion it is sufiicient to reply that the researches of 

 Prof. S. P. Langley, now Secretary of the Smithsonian 

 Institution, show that at the present time no appreciable 

 measure of heat comes to us in that s\ ay, and that probably 



