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shelving has been added, and these facilities have led to a more 

 extended use of the books in this department than has before been 

 possible. This library is already so extensive, and is increasing 

 so rapidly, that a large amount of time is required for the recep- 

 tion, binding, and arrangement of the new works which are 

 added to it. Here, as in other departments of the Museum, the 

 needs are beginning to exceed the means. The rapidity of the 

 increase during the past few years in the number and bulk of 

 geological and mining books issued from the press is indeed most 

 remarkable. 



During the past year, in accordance with the suggestion made 

 in the Sturgis-Hooper Professor's last Report, a Supplement to his 

 work on the United States has been prepared and issued. This 

 work embraces, in about 350 pages, similar in form and style to 

 the original volume, the subjects of population, immigration, and 

 irrigation, much the larger part of the work being devoted to the 

 last-named topic. In this volume the statistics of population are 

 brought down to the latest possible date, including the results of 

 the Census of 1890, the original work having been published just 

 before that was taken. The statistics of immigration include the 

 essential facts down to as late as the end of the first half of the 

 year 1894. 



In the original work to which the present volume forms a sup- 

 plement, the subject of irrigation was not touched upon at all, and 

 chiefly because detailed information regarding it was, so far as 

 the United States are concerned, almost entirely wanting, much 

 the larger portion of the already somewhat voluminous literature 

 relating to this subject bearing dates more recent than 1890. 

 Investigation of the material published by our government, in the 

 reports of the various irrigational and geological surveys, showed 

 that very interesting scientific and economical problems were 

 involved in the irrigation question, and it seemed decidedly worth 

 while that there should be made of it an analytic and critical 

 review from an entirely disinterested standpoint. This, it is 

 believed, has been done, and it is hoped that the volume thus 

 prepared will be found useful to teachers and others interested 

 in the physical geography of the country and the development of 

 its resources. As an Appendix to this volume, there has been 

 added a brief discussion of the question whether changes of cli- 

 mate can be brought about by the agency of man, and on secular 



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