SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE, VOL. XXXIV. 



PLATE XX. 



COPERNICUS AND SURROUNDINGS. PHOTOGRAPHED BY RITCHEY, NOVEMBER 21, 1901, SEVEN HOURS 



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



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



