een 
XXXIT. 
ON THE SELECTION OF SUITABLE INSTRUMENTS FOR 
PHOTOGRAPHING THE SOLAR CORONA DURING 
TOTAL SOLAR ECLIPSES. By ALBERT TAYLOR, 
A.R.C.Sc. (Lonp.), A.R.S.M., F.R.A.S. 
[Read May 16; Received for Publication May 18; Published Juzy 25, 1894.] 
Tue great success obtained by the various parties which observed 
the Total Solar Heclipse of 1893, April 15-16, is extremely 
valuable, not only as giving us a very complete record of the form 
and structure of the Solar Corona at the time of the eclipse, but 
also as indicating the best methods, both photographic and instru- 
mental, for future work in the study of the phenomena of eclipses. 
Although full descriptions and discussions of the results have not 
yet been published, sufficient is known to enable us to form definite 
conclusions on certain hitherto disputed points; and as the next 
observable total solar eclipse is on August 8, 1896, and the organi- 
zation of expeditions to observe it should be commenced at once, 
I have thought it might be useful to briefly indicate, in this paper, 
what I think should be the main considerations guiding the 
organisers and observers of future eclipses. 
There is such a great variety in actinic brightness of the various 
phenomena of an eclipse that it is practically impossible to get all 
of them by one exposure on a photographic plate. As I have 
previously pointed out (“ Observatory,” vol. 16, p. 95), we may 
roughly divide the phenomena into four main divisions—the 
chromosphere and prominences, the inner corona with polar rays, 
the middle corona extending from 10’ to 30’ from the limb, and 
the faint extensions which have been traced, visually, some 5° from 
the limb, and which are only very slightly more actinic than the 
surrounding sky. There are very few difficulties in photographing 
the first three of these portions, but there has been considerable 
discussion as to the best method of photographing the faint 
external extensions of the corona. The eclipse of 18938, April 15-16, 
has added materially to our knowledge on the latter point, and 
has also assisted us in indicating the direction of future work for 
the brighter parts of the corona. 
