FROST— OBSERVATIONS OF THE ECLIPSE. 283 



whereby we could bring into juxtaposition images from the east and 

 west Hmbs of the sun. The scale was about 22 A per mm., and the 

 definition good. The intention was to photograph the green coro- 

 nal line out to about two minutes of arc from the eastern and west- 

 ern limbs of the sun in order to determine, if possible, the rotation 

 of the corona. With clear weather, we should have had as good a 

 chance of making this test as has been had thus far by other expe- 

 ditions. The writer spent ten days at Denver getting everything 

 ready, at the end of May, and the observations were to be made by 

 Professor R. S. Nyswander. Unfortunately the day was com- 

 pletely cloudy in the vicinity of Denver. 



On the observatory grounds at Denver, we had also installed a 

 small coelostat for the direct photography of the corona, utilizing a 

 five-inch objective of twenty-two feet focus, belonging to the Den- 

 ver equatorial. The installation of this apparatus was attended to 

 by Professor Paul Biefeld, of Denison University, who kindly vol- 

 unteered his services. 



The main station at Green River had also been selected in the 

 previous year, when it was visited by Professor Barnard and the 

 writer on a day of extraordinary atmospheric clearness. The 

 weather records for many years seemed to promise extremely well 

 for this station, although there was much bad weather during the 

 six weeks after our camp was established. The elevation of the 

 station was about 6,200 feet. The day of the eclipse was fine until 

 after noon, when white cumulus clouds began to drift across the 

 sky. A large triangular cloud covered the sun at the time of first 

 contact and moved away with aggravating slowness, so that there 

 was a fair question for twenty minutes previous to totality whether 

 or not the sun would be covered by the cloud. Unfortunately the 

 cloud did not drift away until some three minutes after totality. 



Although we had a fine view of the corona and of the brilliant 

 prominences through the edge of the cloud, the spectroscopic obser- 

 vations were very greatly impaired. To me, the visual phenomena 

 of the eclipse were much more impressive than they were in a per- 

 fectly clear sky at Wadesboro in 1900. 



The direct photographs of the corona and prominences were 

 made under Professor Barnard's direction: (i) with the coelostat 



