NO. 5 SOLAR ECLIPSE I919 — ABBOT AND MOORE, 3 



mum corona, equally extensive in all directions, and a sun-spot 

 minimum corona, with relatively short polar streamers and long" 

 equatorial extensions. There was also a great sickle-shaped prom- 

 inence which extended up from the sun to about one-quarter of a 

 radius, then turned sharply round with a very long extension parallel 

 to the sun's surface. Later in the day this prominence was repeatedly 

 photographed with spectroheliographs in the United States, and then 

 extended as a complete arch of very great height and span. 



Taking into account the great length and beauty of the coronal 

 streamers, the splendid crimson prominence throwing its glory over 

 all, and the fact that the eclipse was observed so near sunrise from so 

 great an elevation as 14,000 feet, with a snow-covered range of 

 mountains upwards of 20,000 feet high as a background for the 

 phenomenon, it seemed to the observers to be the grandest eclipse 

 phenomenon which they had ever seen. 



PYRANOMETRY 



The object of the observations with the pyranometer was to obtain 

 the intensity of the sky and solar radiation as the eclipse progressed, 

 and at the time of totality to obtain the intensity of the radiation 

 from the strips of the instrument to space, and compare the latter 

 with similar radiation during the night preceding the eclipse. It was 

 planned to take the night observations every two hours from nine 

 o'clock until daylight, but unfortunately about eleven o'clock a heavy 

 fog occurred which persisted until three o'clock and prevented the 

 observations. Between three o'clock and daybreak there were inter- 

 vals of cloudiness, but at sunrise the sky was perfectly clear, and 

 remained so until nearly the end of the partial phase of the eclipse. 



During the night and during the totality the observations were 

 made with the hemispherical glass removed. At daybreak the glass 

 was put on, and observations made on the scattered sky radiation 

 until sunrise. As soon as the sun rose (about three-fourths eclipsed) 

 the observations were alternated between sky plus the sun and sky 

 alone, the latter condition being arranged by interposing a circular 

 screen of metal to cut off the sun's rays. Both of these intensities 

 were of course measured on a horizontal surface. The units are 



calories ^— f_- . 



min. 



In the reduction of the observations, curves are plotted with hour 

 angles as abscissae, and the intensity of the sun plus sky, and of the 

 sky alone as ordinates. These curves relate both to the day of the 

 eclipse and to the day preceding. By subtracting the sky from the 



