1847
"On Nov. 13th I circulated an Address, proposing to discontinue the
use of the Zenith Tube, because it had been found by a long course of
comparative trials that the Zenith Tube was not more accurate than the
Mural Circle. The Address stated that 'This want of superior
efficiency of the Zenith Tube (which, considered in reference to the
expectations that had been formed of its accuracy, must be estimated
as a positive failure) is probably due to two circumstances. One is,
the use of a plumb-line; which appears to be affected with various
ill-understood causes of unsteadiness. The other is, the insuperable
difficulty of ventilating the room in which the instrument is
mounted.'--On December 20th I circulated an Address, proposing a
Transit Circle, with telescope of 8 inches aperture. The Address
states as follows: 'The clear aperture of the Object-Glass of our
Transit Instrument is very nearly 5 inches, that of our Mural Circle
is very nearly 4 inches.'--I had been requested by the Master-General
of Ordnance (I think) to examine Candidates for a Mastership in
Woolwich Academy, and I was employed on it in February and March, in
conjunction with Prof.
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