450 MR WILLIAM SWAN ON THE 
spider-lines in the eye-piece, which were carefully adjusted to polar and equatorial 
directions.* By this arrangement, the moon’s limb could be readily divided into 
four quadrants, so as to facilitate the estimation of angles of position. 
I employed a position micrometer, expressly devised for the purpose of re- 
gistering the places of the red prominences;} and although we witnessed the 
eclipse under very different circumstances, and I failed to see a number of promi- 
nences which Mr Dawes has figured, yet our observations of the objects which we 
both saw, agree so closely, as to render it probable, that if some efficient means of 
ascertaining angles of position had been generally adopted, the observations would 
usually have been accordant. 
On comparing the different observations, it appears that at least two isolated 
red prominences were seen to the east of the sun’s north point; a long sierra or 
range of red prominences on the sun’s southern limb; two detached prominences 
towards the west of the sun’s vertex ; a large hook-shaped prominence also to the 
west ; a small prominence detached from the moon’s limb, a little to the south of 
the hook-shaped prominence; and two prominences between the large one and 
the western end of the sierra. 
These objects were by no means equally remarkable in appearance; and, ac- 
cordingly, they did not all receive the same share of attention. Probably on this 
account, differences, so great, occur among the observed angles of position, in the 
case of some of the less conspicuous prominences, as to render it impossible, in 
some instances, to determine with certainty to which of them the observations 
refer. I think it then sufficient, to select the hook-shaped prominence already 
noticed, as the object which, on the whole, excited most attention,—whose place 
may thus be assumed to have been the best ascertained,—and of which the ob- 
served angles of position are therefore the most likely to throw light on the nature 
of the red prominences. 
In the absence of information regarding the manner in which the different ob- 
servers ascertained their angles of position, I have given all the observations equal 
weight; and the following table exhibits the several positions assigned to the 
hook-shaped prominence, with the difference of each from the mean of the whole. 
Such of the angles as were reckoned from the sun’s vertex, I have reduced to 
his north point, by means of the latitudes of the stations, and the times of , obser- 
vation, supposing the observations to be made at the middle of the total phase of 
the eclipse. As, however, those data are sometimes only approximately known, 
the reduction of the observed angle is not always quite correct; yet, I believe, the 
error in no case will be found to amount to 1°, so that the comparison of the ob- 
servations is sufficiently exact for the purpose intended. 
* Astronomische Nachrichten, No. 777. Ta elia 
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