306 CAPTAIN L. DARWIN, DR. A. SCHUSTER, AND MR. E. W. MAUNDER 
As regards the drawings, we have the following :— 
Date. 
Year. 
! 
San-spot 1 
numbers. 
April 16 . . 
1874 
The drawings of Mr. Beight and Mr. Degeemann show a dis¬ 
tinctly greater width on the east side. In Miss Alice Hall’s 
drawing the eastern half is less broken up than the western, 
but not broader. In Mr. Wright’s drawing the points of 
the streamers on the eastern side are further apart than on 
the west 
1191 
August 7 . 
1869 
Observers speak of the trapezian form of the corona, which is 
important, as the Sun-spots, though not at their maximum, 
appear in greater number at that time than in either 1882 
or 1883. The drawing of Mr. Meek, given by Mr. Schott, 
seems the only one that is oriented relative to the Sun, and 
here the western side of the Sun is the broad one 
77'6 
August 18 . . 
1868 
The drawings are too uncertain to come to any conclusion, but 
if lines are drawn giving the ends of the extreme rays, the 
rays on the west are in nearly all cases further apart 
42-9 
We have, therefore, not one case in which the eastern side was the broadest in the 
autumn or the western in the spring. 
If we take the time at which the greater eastern width changes to the greater western 
width to be about the middle of June, and middle of December, we should expect that 
in the eclipse which has just taken place the two sides would be about equally developed, 
but if there is a slight asymmetry the eastern side should be the broadest.* 
VI.— The Coronagraph. By Captain Darwin. 
1. Description of the Instrument and its Adjustments. 
The coronagraph was designed by Dr. Huggins as the instrument which would 
give the best chance of rendering it possible to obtain photographs of the corona in 
Sun light. For this purpose a reflector is to be preferred to a refractor, and special 
precautions are taken to avoid internally reflected light. The telescope is of the 
Newtonian form. 
The instrument which I took out is by Grubb, of Dublin, and was mounted on an 
ordinary equatorial stand. The light enters a tube 4 feet long, fitted with numerous 
diaphragms. It then passes into a tube 5 feet 6 inches long (a little less than the 
focal length of the mirror), of about double the diameter of the first tube, the mirror 
* [AvA added July 14,1889.—This prediction has not been verified. In the Eclipse of January 1,1889, 
although there is not much difference between the two sides, the western half is the broader. Neverthe¬ 
less, the considerations in the text are of some use, as they show the importance of taking account of 
the relative position of Sun and Barth in discussing the shape of the corona in different eclipses.] 
