SCIENCE 



A WEEKLY JOURNAL DEVOTED TO THE ADVANCEMENT OF SCIENCE, PUBLISH- 

 ING THE OFFICIAL NOTICES AND PROCEEDINGS OF THE AMERICAN 

 ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 



Editorial Committee : S. Newcomb, Mathematics ; E. S. Woodward, Mechanics ; E. C. Pickering, 



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



Charles D. Walcott, Geology ; W. M. Davis, Physiography ; Henry F. Osborn, Paleontology ; 



W. K. Brooks, C. Hart Merriam, 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. McKebn Cattell, Psychology ; J. W. Powell, Anthropology. 



NEW SERIES. VOLUME XV. 

 JANUARY -JUNE, 1902. 



NEW YOEK 



THE MACMILLAN COMPANY 



1902 



)71759 



