Smithsonian Contributions to Knowledge, Vol. XXXIV. 



Plate XX. 



COPERNICUS AND SURROUNDINGS. PHOTOGRAPHED BY RITCHEY, NOVEMBER ^•}}^^'^:jrl^ "^^^''^^ 



THIRTY-TWO MINUTES P. M.. CENTRAL STANDARD TIME. EXPOSURE, ONE SECOND. 



SCALE, THREE-FOURTHS METER TO MOON'S DIAMETER. 



