THE 



POPULAK scie:kce 



MONTHLY. 



CONDUCTED BY E. L, AND W. J. Y0U3fANS. 



VOL. XIX. 



MAY TO OCTOBER, 1881. 



NEW YOEK : 

 D. APPLETON AND COMPANY 



1, 3, AND 5 BOND STREET. 



1881. 



