446 Chronicles of Science. [ July, 
1856, is the remarkable testimony which they bear to the transparency 
of the atmosphere, and its suitability to telescopic observation at great 
heights above the sea level. At the Radcliffe Observatory Mr. Main 
has been rigorously continuing observations of double stars with the 
heliometer. Most of these stars had been previously examined by 
Struve, the components being of nearly equal magnitudes, varying from 
about the sixth to the ninth ; and Struve concluded that there was very 
great probability that the larger number, if not the whole of them, 
were physically and not optically connected. ‘The results of the Oxford 
observations, thus far, do not confirm this idea, as in the interval of 
more than thirty years which have elapsed since Struve’s observations, 
out of 190 systems examined, very few of the components exhibit any 
considerable motions in distance or position angle. At Cambridge, 
the regular work of an Observatory has been assiduously performed, 
and time has also been found for the ever-varying observations which 
special or seldom recurring phenomena demand, such as cometary 
observations, &c.; although from the absence of a first assistant, Pro- 
fessor Adams feels that the work of the Observatory during the past 
year has been seriously crippled. At the Liverpool Observatory, 
owing to local considerations, meteorology very properly claims 
the chief attention. Their new and most ingenious self-regis- 
tering barometer has been in operation for about twelve months ; 
the sheets on which the record is obtained are removed from the 
cylinder every morning at 9 A.m., and a tracing from the original, 
for the previous 24 hours, is forwarded daily at 10 a.m. to the 
Underwriters’ Rooms, together with an account of the force and 
direction of the wind, the fall of rain, &e. The rating of ships’ 
chronometers, always an important branch of the work of a sea-port 
Observatory, has here largely increased during the last year, and con- 
siderable alterations have been made in the method of giving the 
errors and rates. During the winter months each chronometer is 
exposed for a week to the temperature 50°, 65°, and 80°, alternately ; 
and for whatever time the chronometer may be at the Observatory, the 
error is given at the end of each seven days, together with the mean 
rate and extreme difference of rate between any two days for each 
week. The latter, Mr. Hartnup thinks, shows the quality of a chrono- 
meter better than any other method he has been able to devise. At 
Mr. De la Rue’s Observatory, Cranford, devoted almost exclusively 
to astronomical photography, observations have been made with 
silvered glass mirrors, as a less expensive and more reflective substi- 
tute for the speculum metal mirrors, and there is every reason to 
believe that the time of exposure of the sensitive plate will, by this 
means, be shortened. Mr. De la Rue has continued his experiments 
in enlarging his lunar negative to the dimensions of Beer and 
Madler’s map (38 inches), and has obtained results far surpassing 
those previously recorded. The Ely and Kew Observatories have 
been, during the past year, principally devoted to solar photography ; 
a large number of solar autographs have been taken, and, by a com- 
parison of the pictures taken simultaneously at each Observatory, it 
is anticipated that much information will be gained on the obscure 
