ON THE TOTAL SOLAR ECLIPSE OF MAY 17, 1882. 
259 
the rapid change in the lunar parallax, the calculation of the angles which the line of 
cusps should make with the circle of declination is rather tedious, and would not 
repay the trouble, and without it the orientation of the photographs possesses all the 
necessary accuracy. In adopting 45 minutes as the angle between the shadow of the 
wire and the declination circle, we shall certainly not make an error greater than 
half a degree, and most probably not more than a quarter of a degree. The image 
of the wire lies in the quadrant between the east and the south. 
The backs of the plates in all the cameras were coated with asphaltum, in order to 
prevent photographic irradiation as far as possible, but the prominences and inner 
parts of the corona sent out such a strong light that in spite of this precaution the 
photographic effect encroaches on the disc of the moon. One of the prominences 
appears even reversed on one of the plates which was exposed for about 22 seconds. 
The images of the prominences themselves appear, however, perfectly defined. The 
different times of exposure could not be measured exactly for want of sufficient 
attendance. A very fair idea of the exposures can, however, be obtained from Dr. 
Schuster’s notes made immediately after the eclipse. He wrote :—“ After drawing 
the slide of the spectroscopic camera at the beginning of totality, I immediately 
did the same for the large camera, and called on Mr. Woods to remove the screen, 
which he held up in front. This he, did, noticing that Mr. Buchanan called out 
* 60 at the time. At the time signal ‘ 50 ’ the screen was to be replaced, 
thus giving an exposure of 10 seconds. Mr. Woods was, however, a little late in 
answering to the signal, and I believe that 11 seconds would not be a bad estimate 
/or the exposure of this plate. There was no record made of the time at which the 
second plate was actually exposed, but experience had shown that it took about 
7 seconds to change a plate in this camera, and as the exposure ended at the time 
signal previously fixed upon, I think we may take the exposure of this plate to 
have been 23 seconds within one second of error. The third plate was to be 
exposed for 3 seconds ; these were estimated by Mr. Woods, and as he has had 
much practice in exposing photographs, this time was probably correct within narrow 
limits.” 
The body of the moon appears on the photographs bordered by a well-defined black 
line, out of which the prominences are seen to rise. It must be borne in mind that , 
the radius of the moon during the last eclipse was only slightly larger than that of 
the sun, so that even in the middle of the eclipse the brightest parts of the corona, 
and perhaps even the upper layers of the chromosphere, were visible. The inner 
parts of the corona, and especially the prominences, are over-exposed in all the 
photographs, but in that one which had three seconds’ exposure all the details up to 
the body of the moon are well shown. 
As regards the corona, we are especially struck with the irregularity of its shape. 
A close connexion between the outline of the corona and the state of the sun’s surface 
is now placed beyond doubt. The corona, as seen in Colorado during the summer of 
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