172 G. F. Becker—Temperature and Glaciation. 
glaciers cannot in fact have occurred when the glacial isotherm 
touched the top of the highest mountain peak; for though the 
meteorological conditions were eminently favorable, insufficient 
space was afforded for the accumulation of névé. As the iso- 
therm descended the slope of the mountains, the topographical 
condition became more favorable, while the meteorological ten- 
period of maximum glaciation. It is by no means to be in- 
out the year, and in spite, too, of an active circulation of alr 
Glacial ice even accumulates in artificial openings in localities 
far removed from any mountain glacier. The bottom of the 
Dannemora iron mine, for example, an immense open pit some 
500 feet deep, is covered with ice to a depth of many feet 
