THE 



POPULAR SCIENCE 

 MONTHLY 



Established in 1872 by Messrs. D. Appleton 

 and Company, and Dr. E. L. Youmans 



The Popular Science Monthly is published by Messrs. McClure, 

 Phillips and Co., New York, and edited by Prof. J. McKeen Cattell, of 

 Columbia University, with the assistance of Dr. E. L. Thorndike, also 

 of Columbia University. 



The fifty-six volumes of the journal already published have per- 

 formed an important service for the advancement and diffusion of 

 knowledge. Its issues have each month carried to all parts of the 

 country reliable information in regard to the advances of science, widen- 

 ing and deepening everywhere an intelligent interest in scientific sub- 

 jects. The journal represented the doctrine of evolution before its 

 tenets were generally accepted; it has done much to diffuse knowledge 

 of physical science and of the applications of science; it has been a 

 factor in the development which has reformed our entire educational 

 system from the kindergarten to the university; its contributors have 

 included many of the world's greatest men of science. 



The Popular Science Monthly aims to represent fully and ac- 

 curately the advance of science; to permit the leading men of science 

 to bring their work before the largest public; to set a standard to the 

 popular press in its treatment of scientific topics; and to secure the 

 general interest in science that is needed for its adequate recognition 

 and support. 



A journal with these aims is necessary, both to men of science and 

 to the general public. It brings men of science into contact with those 

 whose sympathy and help they need, while it enables the general public 

 to follow intelligently the progress of science and its contributions to 

 civilization. This double service of The Popular Science Monthly 

 is fully recognized; it has the largest circulation of any scientific journal 

 in the world, and it is conducted with the support of the leading men 

 of science, including in America: 



Cleveland Abbe, Professor of Meteorology, United States Weather Bureau. 



Cyrus Adler, Librarian, Smithsonian Institution. 



Edward Atkinson, Boston. 



W. O. Atwater, Professor of Chemistry, Wesleyan University. 



J. A. Allen, Curator of Vertebrate Zoology, Am. Museum of Natural History. 



L. H. Bailey, Professor of Horticulture, Cornell University. 



Marcus Baker, United States Geological Survey. 



J. Mark Baldwin, Professor of Psychology, Princeton University. 



Lewellys F. Barker, Professor of Anatomy, University of Chicago. 



