THE 



POPULAR SCIEl^CE 



MOI^THLY. 



GONDUGTED BY E. L, AND Y/. J, YOUMANS. 



VOL. XXV. 



MAY TO OCTOBER, 1884. 



NEW YORK : 

 D. APPLETON AND COMPANY, 



1, 3, AND 5 BOND STKEET. 

 1884. 



