250 ' THE SOLAR ECLIPSE. : 
of d and c in equal intervals of time the following values, which, however, 
represent neither an increasing nor a diminishing series, namely : 
d c 
25° 50! 55° 50! 
20 20 56 20 
(‘T'wo observations lost.) 
20 20 56 20 
23 20 53 20 
while the latter measured three altitudes of the protuberance a, of which the 
first is doubtful, and, as Airy has circumstantially shown, (58,) if the correction 
required by the observer himself be adopted, would be against the hypothesis 
of solar clouds; but if the correction be not adopted, would be am favor of that 
hypothesis. By indirect methods, comparing with the position of the solar 
crescent, Bruhns (31) (102) obtained two position-angles of the protuberance d, 
which he was able to follow from 2 minutes before until 8 minutes after the 
total eclipse, and found that in an interval of 13.7 minutes the angle of position 
had diminished 26.°3, an argument of weight in favor of the assumption of 
solar clouds. On the other hand, Von Feilitzsch (44) (45) determined by 
measurement the diminution of the protuberance a in one minute to be 45”, 
and Plantamour (47) found it more than 30’, while it should have amounted 
to only 23”. The latter pointed out also that the floating cloud ¢ vanished 
before it could be reached by the advancing moon’s limb; and entirely similar 
results, pronouncing decidedly against the assumption of solar clouds, were 
obtained by Mr. 'Thiele, (106,) who compared the altitudes of the protu- 
berances measured at definite instants with the times of their disappearance, 
and thence computed the diminution of altitude. 
Besides these measurements, there are in the material before us no other 
numbers which could lead to a decision. ‘The progress of the eclipse, however, 
produced in many observers, among them Messrs. Plantamour, (47,) d’ Arrest, 
(107,) Legrand, (46,) Goldschmidt, (41,) (42,) &c., the definite impression 
that the changes of altitude did not proceed with uniform velocity, and my 
own perceptions agree with this. On the other hand, Mr. Secchi (60) (61) 
brings up the circumstance that the colors of the protuberances were very dif- 
ferent from the interference colors exhibited in optical experiments. 
Since the central shadow passed over the whole distance from the northern 
to the southern coast of Spain in ten minutes, the protuberances considered as 
solar clouds should have appeared at all the stations the same in form and 
colors. Now, upon comparing together the drawings and descriptions of the 
different observers, it will be always possible, by interpreting and completing 
deficiencies with considerable freedom, to produce a similarity; but without 
such interpretation and completing, there is certainly to be found no’ satisfac- 
tory agreement at all. 
Definite resting points might be gained by comparing the forms which the 
same observer saw at different moments during the totality; and yet, in this 
respect, we find contradictory testimony, for, while Bremiker (30) could per- 
ceive no changes, Messrs. Plantamour, (47,) Von Feilitzsch, (45,) Bruhns, (31,) 
and Goldschmidt, (41,) (42,) did observe changes of form and color in sey- 
eral protuberances. I noticed the same thing, with all certainty, in the pro- 
tuberance a. 
With regard to the corona, and the rays therein contained, the observers ap- . 
pear generally to have attained to the conviction that they do not belong to the 
sun, but are occasioned by interference at the moon’s limb, and partly also by 
the vapors in our atmosphere. 
The question whether the same rays were seen at the different stations cannot 
be decided with definiteness, for, while in the drawings at Pobes and Tarazona 
' 
