HVPOTHESIS OF CAUSE OF GLACIAL PERIODS 787 
relations, in the geographic features, and in the meteorological 
inferences drawn from them. The most that could be hoped 
from an attempt to explain so extraordinary phenomena in so 
imperfect a condition of the data is to suggest the general direc- 
tion in which, perchance, the truth may ultimately be found to 
lie. T. C. CHAMBERLIN. 
