SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE. 



180 



ON THE CONSTRUCTION 



SILVERED GLASS TELESCOPE, 



FIFTEEN AND A HALF INCHES IN APEETURE, 



ITS USE IN CELESTIAL PHOTOGRAPHY. 



BY 



HENRY DRAPER, M.D., 



PEOFESSOB OF NATURAL SCIENCE IN THE UHIVEKSITV OF NEW YOKK. 



[accepte-d fob pcblioation, januaby, 1864.] 



