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. Still, while acting as a pioneer in the matter, it will be seen that I have only attempted to expose the main outlines, as my age and failing health will not permit me to enter into the voluminous details necessary for a full explanation. In order to show why my attention has been turned to the great climatic changes which have taken place during past ages, and now threaten the future, I will repeat the introduction of my earlier publication, wherein I wrote that “the reason why I have undertaken to explain the causes which have brought about the warm and cold epochs is because of my being unable to harmonize the several theories4 that have been published with the general mode of action which nature pursues to-day. Having ............