Moulton, Forest Ray, 1872-1952 · New York, The Macmillan company · leaf 322
even to-day astrono-mers can recognize the objects which these men observedand drew. Some of them are shown in Fig. 103, which is a CH. IX, 170] THE PLANETS 275 series of 9 photographs, taken one after the other at shortintervals, by Barnard, at the Yerkes Observatory. Bycomparing observations at… … Fig. 10.3. —Mars. Photoffraphed bv Barnard with the 40-inch telescope ofthe Yerkes Observatory, Sept. 28, 1909. and Cassini soon discovered that Mars turns on its axis ina perioti of a httle more than 24 hrs. By comparing theirobservations with those of the present day it is found thatits period of…
Astronomy
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