532 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



and can be traced a distance of two diameters of the sun, over a 

 million and a half miles. Those about the poles, the so-called polar 

 fans, are very distinct and strong. At the north pole, they seem to 

 be longer and not so sharply curved, and appswently more numerous, 

 while at the south pole they are sharply curved, especially toward 

 the west. The western half of the corona is full of detail. Three 

 distinct, petal-shaped extensions radiate from the center, covering 

 an arc of about 120 degrees. One quickly thinks of the appearance 

 of the petals of a white wild rose. This petal-like formation has 

 been observed in many previous eclipses, but its structure has not 

 been so apparent. It is made up of these bright rays which seem 

 to bunch around the sun-spot zone. The dark rifts described in our 

 textbooks are very probably the spaces between these petal-like for- 

 mations. 



Two slightly curved rays, extending from the southwest quad- 

 rant, cross at a very definite, measurable angle. The eastern stream- 

 er has many straight rays, a little brighter than the general corona, 

 extending through it at small angles to its general direction. Three 

 remarkably bright prominences stand out over the moon's disc at 

 approximately 120 degrees apart. One of the most remarkable fea- 

 tures, and, so far as I know, one which has not been observed in 

 previous photographs, is the arching of the corona around the 

 prominences. The upper eastern prominence, which is the highest, 

 has three arches, one above the other, but not in the same plane. 

 The lower western prominence has still larger arches, but slightly 

 fainter. A small prominence is located near each pole of the sun. 



The 40-second and 11 -second exposures were sent to Professor 

 Barnard at Yerkes Observatory, who very kindly consented to de- 

 velop them for me. As was expected, the 40-second plate was badly 

 overtimed, indeed to such an extent that the prominences were re- 

 versed. Professor Barnard stated in a letter to me that he did not 

 know of a similar occurrence in eclipse negatives. The corona is 

 nearly lost in the sky effect. 



The 11-second plate is much better, but not as good as the shorter 

 exposures. 



Plate No. 5 is quite interesting. As noted above, I stopped the 

 exposure promptly at the 86th second, although the signal to stop 

 had not been given by the timer. The chromosphere is distinctly 

 visible at the western edge of the moon's disc and is reversed, that 

 is, light in the negative. At either end of the arc of the chromo- 

 sphere is a prominence. The one at the southern end is extremely 



