The Sun.
London, England, 1863-07-29 00:00:00

Cambridge 'University Observatory.

It appears that the meridian observations made at
this establishment during the past 12 months com-
prise, in addition to those of the fundamental stars,
observations of the stars which were used for com-
parison with comet 2, 1861, and comet 2, 1862; obser-
vations of the sun near the summer and winter sols-
tices, and the autumnal and vernal equinoxes ; obser-
vations of the planets Jupiter and Neptune, and circle
observations of Mars and of the stars selected by
Dr. Winnecke to be compared with the planet
in declination, with a view to the determination of
its parallax. The total number of transit observa-
tions since the date of the last annual report is 924,
and the number of circle observations 656. The
equatorial observations comprise a series of observa-
tions of comet 2, 1862, and comets 2 and 3, 1863,
and a series of comparisons in R.A. between Mars
and neighbouring stars, taken on both sides of the
meridian, according to the plan described by the
Astronomer Royal in the monthly notice. Charts
drawn on a large scale were prepared of all the stars
near the path of Mars, which was contained in Dr.
Argelander's valuable survey of the northern
heavens, and the stars of comparison were selected
from these. The weather was unfavourable
during the course of these observations, so that,
although they were made on 20 different nights,
not more than seven sets of corresponding
morning and evening observations could be ob-
tained, in which 49 comparisons were taken on
the eastern and 48 on the western side of the meri-
dian. The total number of those comparisons of
Mars with neighbouring stars amounts to 192, of
which 124 were taken on the eastern and 68 on the
western side of the meridian. A few observations
have been made of occultations of stars by the moon
and of eclipses and other phenomena of Jupiter's
satellites. Several new arrangements have been
made in reference to some of the instruments, The
old lever counterpoises of the transit instruments
were removed some years since by Professor Challis,
and were replaced by spring counterpoises in order
to allow the use of micrometer microscopes adjusted
for viewing dots placed on the end of the pivots so
as to afford means of eliminating any errors arising
from the form of the pivots. The spring, counter-
poises, however, acted in an unsatisfactory man-
ner, as the pressures which they exert are con-
tinuallywith changes of temperature.
Profess ry
Professor vAadaminsghas therefore removed them and
restored the lever counterpoises; the apparatus for
examining the form of the pivots may now be used,
however, while the counterpoises are in action. The
pendulum of the transit clock has been put in good
order. In consequence of the varying length and
weight of the declination, rods of the Northumber-
land equatorial corresponding to different north
polar distances, a series of adjustable weights has
been introduced, by means of which, for any given
value of north polar distance, the instrument may
be very nearly balanced in all positions. Four
new verniers have also been introduced, for reading
off the hour circle of this instrument. Some altera-
tions have been made at the eye-end of the Nor-
thumberland telescope, in order to render it pos-
sible to use eye-pieces, giving a larger field of view,
and a small position circle has been applied to the
finder, so as to give the means of measuring
approximately angles of position. On the Jones
equatorial being dismounted, for the purpose of being
examined, several of the springs which relieve the
pressure on the lower pivot were found to be broken,
which materially interfered with the freedom of mo-
tion of the instrument about its polar axis, The
microscopes were also out of order. The instrument
has now been put into working order by Mr. Sines,
and some amendments have also been introduced
n
into the dome. The Graham clock has been
roughly restored by Mr. Frodsham.

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