ESTABLISHED BY EDWARD L. YOUMANS. 



THE 



POPULAE SCIENCE 



-*^S^'^ 



EDITED BY WILLIAM JAY YOUMANS. 



VOL. XXXIX. 



MAY TO OCTOBER, 1891. 



** Jf 3 <>^4^ 



NEW YORK : 



D. APPLETON AND COMPANY, 



1, 3, and 5 BOND STREET. 



1891. 



