SOLAR RESEARCH AT THE MOUNT WILSON OBSERVATORY

The activity of the Sun during the present sun-spot period, which reached its maximum about August, 191 7, has offered many opportunities for observing and recording exceptional phenomena in the regions occupied by sun-spots. Some of the observations have been made and recorded visually, but the majority are photographic. The instruments employed in the solar work during the last three years are the two tower telescopes. The Snow horizontal telescope has been dismantled and remodeled, but owing to the activities of our instrument shops in turning out war work for the government during the past two years the completion of the changes in the spectroscopic equipment for this telescope has been temporarily deferred.

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