Smithsonian Contributions to Knowledge. Vol. XXXIV, 



Plate XXIII. 



MARE IMBRIUM AND SURROUNDINGS. PHOTOGRAPHED BV RITCHEV, NO\-EMBER 21, lliOl, 



SEVEN HOURS THH^TY-TWO MINUTES P. M., CENTRAL STANDARD TIME. 



EXPOSURE, ONE SECOND. SCALE, ONE-HALF METER 



TO MOON'S DIAMETER. 



