THE explanations given in the following pages, in which I have sought to
show the manner in which an ice age is being brought about, is an extension of a
treatise on “The Cause of Warm and Frigid Periods,” which I published in a
small edition in 1894. And, from the small number of copies circulated, only a
few came to the hands of persons particularly interested in such matter. Yet there
were instances of its having proved of special interest to persons celebrated for
their geological attainments, and also to instructors in physical geography.
Besides, it received considerate notice in some of the leading reviews. Being
thus somewhat encouraged, and thinking that the subject was too important to be
neglected, I have given it further study during the last year, and meanwhile have
obtained additional information from recent discoveries which has served to
corroborate my views. Hence I have been able to be more explicit in my
explanations in the present volume than in my earlier writings.