Vol. LXVI. No. 4 FEBRUARY, 1905 



THE 



POPULAR SCIENCE 

 MONTHLY. 



EDITED BY J. McKEEK CATTELL 

 CONTENTS 



An Address on Astrophysics. Professor W. W. Campbell . . . 297 



The Metric System of Weights and Measures. Professor E. A. Kennelly 319 



A Botanical Laboratory in the Desert. Professor Francis E. Lloyd . 329 



How Immigrants are Inspected. Dr. Allan McLaughlin 357 



On the Relations of the Land and Fresh- Water Mollusk-Fauna of 

 Alaska and Eastern Siberia. William Healey Dall .... 362 



Examinations, Grades and Credits. Professor J. McKeen Cattell . . 367 



Shorter Articles and Correspondence : 



De Morgan and Characteristic Corves of Composition : Dr. T. C. Mendenhall . 379 



The Progress of Science : 



Convocation Week in Philadelphia ; The American Association ; The Presidential 

 Address ; The Affiliated Societies ; Scientific Items 380 



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