452 MR WILLIAM SWAN ON THE 
Mr Dunkin and Mr Snow, who were both stationed near the observatory in 
Christiania, differ by 20° in their observations of the same remarkable object. 
Lieutenant Perrersson, Mr Avie, Mr Atry, and myself, were all situated within 
a circle of about two miles radius, yet while Lieutenant Perrersson’s observation 
of the hook-shaped prominence agrees almost exactly with mine, Mr Apis, and Mr 
Airy differ from us by 13° and 22° respectively. Here then, where, even on the 
hypothesis that the prominences are merely optical phenomena, we should expect 
identity of position, we meet with alarming discrepancies. 
On the other hand, although Mr Dawes was stationed above 100 miles from 
Goteborg, the position he assigns to the hook-shaped prominence, agrees almost 
exactly with that given by Lieutenant Perrersson and by me; and Mr Hinp also, 
who was near Mr Dawes, differs from us by less than 8°. Now, as Goteborg was 
near the middle of the moon’s shadow, while Ravelsberg, where Mr Hinp and Mr 
Dawes observed, was near the southern edge of the shadow, the eclipse was seen 
at the two stations under widely different circumstances; and on the optical 
hypothesis, we might expect great discrepancy in the angles of position. The 
coincidence in the observations is therefore strongly in favour of the view that 
the prominences are material objects; and this conclusion is strengthened, when 
it is borne in mind that the hook-shaped prominence being seen near one of 
Mr Dawes’s cross-wires, its position could be estimated with great accuracy, 
and my angles of position were actually measured ; so that the close agreement of 
our observations is by no means to be attributed to chance. The only other person, 
so far as Iam at present aware, who has determined the position of the hook- 
shaped prominence by actual measurement, is M. Wicumann, who observed the 
eclipse with the Konigsberg heliometer. He states his determination as some- 
what doubtful; but it agrees so well with that of Mr Dawes, and with my own, 
as to render it highly probabie that the positions of that prominence, as seen 
from stations nearly 400 miles distant, were identical. The following table con- 
tains the observations to which I have now referred; and I have added those 
of the spots on the sun, in order that it may be seen that the discrepancies 
in the observed positions of the prominence scarcely exceed those in the positions 
of the spots. As the spots are objects which, while they last, have their positions, 
if not permanent, at least subject only to small and slow changes, we cannot 
attribute the variations in their observed positions to change of place. We must 
therefore refer these discrepancies to errors of observation ; from which it follows 
inevitably, that the variations in the observed positions of the prominence, as they 
scarcely exceed those in the positions of the spots, are also within the limits of 
errors of observation. 
The agreement of the measured angles of position of that object appear, in- 
deed, sufficiently close, when we advert to the circumstance that it must have 
* Astron., Nachrichten, No. 787, p. 323. 
el Ate. eee 
