HYPOTHESIS OF CAUSE OF GLACIAL PERIODS 685 
timesratess at the other extreme, that is, that the. agencies 
necessarily act too rapidly to correspond to the phenomena. Of 
course, in the final adjudication of the hypothesis, it will be 
necessary to show that its-time rates not only might correspond 
to the time rates of the phenomena, but that they did so, but 
this is a labor of the future, and is obviously dependent upon a 
very notable extension of precise knowledge, which it is the 
purpose of the hypothesis to aid in calling forth. It is sufficient 
here to show that reasonable postulates, based on a reasonable 
estimate of the phenomena, fall within compatible limits. 
T. C. CHAMBERLIN. 
(To be continued.) 
