THE SOLAR ECLIPSE. 249 
Littrow (12) have pronounced very decidedly in favor of solar clouds, and Mr. 
Von Feilitzsch (22) for phenomena of interference. The detailed theoretical 
references given by the latter deserve very special attention, and include all 
the optical phenomena of total eclipses—the corona, the rays in the corona, 
and the protuberances. For producing the latter there are assumed at the 
moon’s limb isolated conical elevations of about 500 feet altitude azid base, 
which are yet so small that they could not be seen with telescopes magnifying 
300 times; and it is also shown that the same theoretical development explains 
the origin of an zso/ated protuberance. if we assume at the moon’s limb a very 
high isolated mountain summit. With regard to the hypothesis advanced by 
myself, (2,) that the colors of the protuberances are produced by inflexion of 
light at the moon’s limb, but their form by small masses of vapor floating in 
our atmosphere, this has been set aside by the circumstance mentioned above, 
that the same protuberances were seen at different places. Nevertheless, I 
cannot yet entirely give up the opinion that the vapors of an atmosphere—that 
is, the condensations caused by reduction of temperature next to the inmost 
shadow—do exercise a very considerable influence upon the phenomena of total 
eclipses, and especially upon the forms of the protuberances. 
If we examine how the opinions relative to these questions stand now after 
the observations of the total.solar eclipse of 1860, we find the vote comes out 
nearly as follows: 
In favor of solar clouds, more or less decidedly, are—Messrs. Airy, Le 
Verrier, Secchi, Aguilar, Struve, Madler, Gautier, Bremiker, Gilliss, Winnccke, 
Petit, Prazmowski, Lespiault. 
In favor of interference phenomena are—Messrs. Plantamour, d’Abbadie, 
Marquez, Legrand, Faye, Lamont. 
A preponderating number have, therefore, declared themselves in favor of 
the first opinion. Hereby we must not omit to consider that every one who 
desires to combine different observations of a solar eclipse into a single result > 
is compelled, at the same time, to enterpret critically and to supply deficiencies. 
In the shortness of time and the incompleteness of the apparatus no observer 
can completely and accurately take in the whole phenomenon, and therefore 
an interpretation and completion seems necessary and justified. But thereby 
the deciding ground becomes so far doubtful, that probably the greater part of 
the non-participating astronomers will consider the case as not yet ripe for 
decision. 
The criteria according to which we must decide are very simple. Sup- 
posing that the moon moves over the sun exactly from west to east, then the 
protuberances, whether solar clouds or caused by interference, will first appear 
in the east, and gradually diminish in size, will come out later in the west and 
increase in size; while upon the north and south the magnitude must remain 
unvaried. If the protuberances are solar clouds, there are yet to be added the 
special conditions : 
1. That the diminution of altitude in the east and the increase in the west 
must exactly correspond to the relative motion of the moon. 
2. That the protuberances must remain unchanged in form and color. 
3. That with the northern and southern protuberances there must be changes 
of the angles of position corresponding with the relative motion of the moon. 
Applying these propositions to the several protuberances mentioned above, 
it appears that with d the altitude should have remained unchanged; but the 
osition-angle should in each minute have diminished about 1.°9. That, 
a ana the protuberance ¢ should have diminished by 14”, and a by 23!’ 
in each minute, and the protuberance g should have increased 24”, f 26’, and 
e 20” in the same time. , 
Direct measures, with reference to the given criterions, were made by Messrs. 
Airy (88) and d’Abbadie, (57,) and the former found for the position-angles 
