$3.00 a Year. 25 cents a Number. 



TWENTY-NINTH YEAR ^ 



THE 



Populae Science 

 Monthly 



Edited by Professor J. flcKBEN CATTELL 

 of Columbia University 



With the Co-operation of Leading American Men of Science. 



TT is fortunate for American science that America's leading scientific 

 periodical should continue to be published under favorable auspices. 

 Since its establishment by Messrs. D. Appleton & Company and the 

 late Dr. E. L. Youmans in 1872, this journal has been so important a 

 factor in the distribution of scientific knowledge that it seems almost 

 useless to call attention to the great names which have been associ- 

 ated with it during the past twenty-eight years — to such names as 

 those of Darwin, Huxley, Spencer, and many others, to whose works 

 many Americans were first introduced through its pages. 



In the future, as in the past, THE POPULAR SCIENCE MONTHLY 

 will afford an accurate and authoritative record of the progress of con- 

 temporary science, and besides being indispensable to the professional 

 investigator, it will seek to secure that popular interest and support 

 which are of essential importance to the cause of scientific progress. 



THE NEW EDITOR 



Dr. JAMES McKEEN CATTELL, Professor of Psychology in Columbia 

 University, and Editor of Science, occupies a well-known posi- 

 tion of distinction among American men of science. Dr. Cattell is 

 thoroughly familiar with the needs of the general public, and will 

 have these in view as well as those of special scientific knowledge. 

 He will be assisted in the editorship by Dr. E. L. Thorndike, of Colum- 

 bia University. 



