SCIENCE 



A WEEKLY JOURNAL 



DEVOTED TO THE ADVANCEMENT OF SCIENCE 



Editorial Committise : ^ Nevvcomb, Mathematics ; E. S. Woodward, Mechanics ; E. C. Pickbeinq, 



Astronomy ; T. C. Mendenhall, Physios ; R. H. Thurston, Engineering ; Ira Eemsen, Chemistry ; 



Joseph Le Conte, Geology ; W. M. Davis, Physiography ; Henry F. Osboen, Paleontology ; 



W. K. Brooks, C. Hart Mebeiam, Zoology ; S. H. Scudder, Entomology ; C. E. Bessey, 



N. L. Britton, Botany ; C. S. MiNOT, Embryology, Histology ; H. P. Bowditch, 



Physiology ; J. S. Billings, Hygiene ; William H. Welch, Pathology ; 



J. McKeen Cattell, Psychology ; J. W. Powell, Anthropology. 



NEW SERIES. VOLUME XI. 



JANUARY -JUNE, 1900. 



NEW YOEK 



THE MACMILLAN COMPANY 



1900 



