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POPULAR SCIENCE REVIEW. 
planets, each observer taking a particular district of the ecliptic, and some 
good results followed the attempt. These were, however, surpassed by the 
individual exertions of later years — each planet-seeker working promis- 
cuously. Now, however, that the list has attained such dimensions, the 
question of variable stars is a favourable field for division of labour. 
Mr. Knott finds that the variable star R. Vulpeculse may reasonably be 
classed under the head of regular variables, although he at first suspected 
some irregularities in its change of brightness. He observed it at its 
brightest point, 18G1, Dec. 80, and 1862, Oct. 4, being only 34 and 4 days 
later than the times predicted by Dr. Winnecke, and giving a period of 
138J days. 
The variable star U. Geminorum, which Mr. Pogson describes to be 
subject to such remarkable changes, viz., from the 0th to the 13th May, in 
intervals from nine to fifteen seconds, still continues its eccentric course. 
Mr. Baxendell observed it on Dec. 26, 1862, of the 104 mag., when it 
should have been below the 1 4th ; on the 20th and 30th it was invisible. 
Air. Knott assumes it from observation to have been invisible, or below 
12J mag., on Dec. 20. 
i Stellar Spectra.— This subject appears to be in rather a confused state at 
present, for Professor Donati finds different lines from Frauenliofer in 
nearly all the stars; and a careful American experimentalist again differs 
from Donati. The latter astronomer, however, made use of the micro- 
meter in determining their places, and he thinks that if only eye-measures 
are employed one may be easily deceived, owing to the extreme faintness 
of the colour, in which the reddish tinge is the only one visible. Frauen- 
hofer finds a fine line in the green, Donati in the blue. The former finds, 
between the yellow and red, a line in Pollux, Capella, Alpha (Orionis), and 
Procyon, which the latter has never seen. Frauenliofer found Procy on 
very difficult, whilst Donati found it easy. As the Astronomer Royal has 
instituted a series of experiments we may expect these points to be speedily 
determined. 
Photographs of the Moon. — Mr. De la Rue has succeeded in obtaining 
an enlarged picture of the moon, equal in size to the great map of Beer 
and Maedler, viz., 38 inches in diameter ; the original negative being 
only one inch in diameter. There must be a combination of very 
favourable circumstances in order to obtain a good picture — “ atmosphere, 
collodion, instrument, driving clock, all must be perfect.” Mr. De la Rue 
has taken four hundred negatives during the last five years, yet of those 
only about twenty are capable of producing a perfectly sharp photographic 
record. The beautiful specimens which we have seen at the Exhibition 
prove that this vast amount of labour has been well rewarded. 
The fine specimens of lunar photography, accompanying Dr. Vengeur 
d’Orsan’s book on the moon, were much admired when they first came 
out ; but circumstances have since occurred which have in a great degree 
disturbed and affected this opinion of their merits, and doubts are expressed, 
not as to their accuracy, but as to their originality. If they be original, 
it will of course be a simple matter to produce others not bearing such a 
resemblance to those of Mr. De La Rue, which are known to be bond fide 
pictures. 
