511 
SCIENTIFIC SUMMARY. 
QUARTERLY RETROSPECT. 
ASTRONOMY. 
The Missing Nebula . — “ The lost Pleiad” has at length reappeared (although 
■with greatly diminished lustre), hut it has hitherto been only visible in the 
gigantic Pulkowa refractor. Having received information of its disappear- 
ance in December, 1861, M. Otto Struve lost no time in turning his great 
telescope to that part of the heavens, and on the first favourable night (De- 
cember 29, 1861), after the usual few preliminary adjustments of the eye (in 
adapting it to the detection of faint objects), he had the pleasure of distinctly 
recognizing u some traces of nebulosity to the south of a star of the eleventh 
magnitude.” M. Winnecke confirmed the observation, — assigning to the 
nebulosity the same position as M. Struve. Three months of unfavourable 
weather at St. Petersburg followed this bright night ; and it was not until the 
evening of March 22 that any further opportunity occurred of inspecting the 
object. On this latter occasion, however, the correctness of the previous 
observation was fully established. The nebula appeared considerably brighter 
than in December, so much so as even to allow a slight illumination of the 
field of view. The sketch given by M. Struve fully agrees with that observed 
by the -writer of this notice in 1855, showing a small elliptical nebula of two 
minutes in length, much brighter at one extremity than the other. The 
celebrated observer who detected the reappearance of the nebida, is of 
opinion that it is variable in lustre, — that its light had considerably 
increased between December and March, although he thinks that the 
extraordinary transparency of the atmosphere in the latter month may 
have added to the contrast. As an example of contradictory evidence, 
and of the little reliance to be placed on negative evidence, it may be 
stated that M. Julius Schmidt (of the Athens Observatory) was looking 
for the nebula on the nights of March 19, 20, 21, 24, and 25, in a per- 
fectly clear sky, but not the least trace could be perceived of it. On March 
26 and 27 the same result happened, although the glasses of the refractor 
were cleaned in the meantime, and precautions were taken to hide the light 
of some small stars in the field. The sharpness of M. J. Schmidt’s vision 
and his conscientious accuracy are so well known, that this is not of the least 
detriment to his talents. It is of the statements of those observers who see 
everything, with the smallest telescopes and under the most adverse circum- 
stances, that we are suspicious. M. Schmidt had a smaller telescope than 
M. Struve — had he had the assistance of a sixteen-inch object-glass we have 
no doubt but that he would have succeeded ecprally well. M. Schmidt adds 
