ME. WAEEEN DE LA EUE ON THE 
angularly divided concentrically with the sun, and a scale of minutes and seconds of arc 
etched, starting from the sun’s limb, by which means the prominences were referred to 
the sun’s centre, and their angles of position and heights above his periphery could be 
read off with a fair degree of accuracy. 
In the three Plates, XIII., XIV. and XV., a wrong correction was, however, applied 
for the errors of the wires in determining the zero of the angular divisions, namely +23' 
for both totality pictures, instead of +15'-5 for the first totality picture and +16''5 
for the second ; so that in taking angles of position of the prominences, the readings on 
Plate XIII. must be corrected by applying the number — 7''5 ; those on Plate XIV. by 
applying the correction — 6'-5, and those on Plate XV. by applying — 7'-0. 
Moreover, a small error in determining the centre in Plate XIV. also interferes Avith 
the absolute correctness of the position-angles and of the heights of the prominences 
above the moon’s periphery. Subsequently to this being etched, I discovered the fact 
that the centre should have been placed about 5" of linear space nearer 270°, in a direction 
from 90° to that point, and 4" nearer 360°. The angular positions of some of the prin- 
cipal prominences, determined by measurement of the original negatives, will be herein- 
after given, so that no difficulty will be experienced in correcting the position of the 
other prominences as read off from the Plates. The prominences in these Plates are 
represented in their natural (erect) position, and this is also the case vrith the sun-spots 
in Plate XV. ; the position-angles are laid down from North towards East. The North 
point (360°) is consequently at the top, the East point (90°) is on the left hand, the 
South point (180°) is at the bottom, and the West point (270°) on the right hand. 
In order to facilitate reference to the prominences, I have designated them on 
Plate XV. by capital letters, commencing with the prominence situated at right angles 
to the path of the moon across the sun’s disk, which I call A; and I then follow on 
towards the east with the other capital letters, the small letters being employed, either 
alone, or with one or more dashes, to mark the subordinate parts. 
The three principal sun-spots are marked «, J, c in the order of increase of their 
several position-angles. 
In Plates XIII. and XIV. the details were drawn in on the back of the glass plate, 
and the collodion pictures still remain intact ; Plate XV. was drawn on the face of the 
enlarged positive, which had been taken intentionally in a reversed position, by reversing 
the original negative in the copying-camera. The correction in the position of the glass 
negative on account of its thickness was duly made ; that is to say, the totality pictures 
having been copied with the collodion turned towards, and the sun-pi ctm'e with the 
collodion turned from the lens, the collodion was in this way carried from tlie lens a 
quantity equal to the thickness of the glass plate. The holder supporting the original 
negative was therefore moved towards the lens a similar quantity, and the relative sizes 
of the pictures, as a matter of course, remained undisturbed. 
Plate XV. will be found useful as an index map of the prominences, and will facilitate 
comparisons of the results obtained by the various astronomers who observed the eclipse. 
Moreover, the position of the sun’s axis being given on it, an idea may be formed by 
