THE EOYAL ARTILLERY INSTITUTION. 
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( b ) By a button at eye-end of telescope, from wliicb tlie motion is 
carried by a system of bands to a pulley on same right 
ascension slow motion screw. 
( c ) Or by an endless cord from a pulley on clock shaft, which acts on 
a pair of differential wheels, producing a slight acceleration or 
retardation of clock’s rate. 
[N.B.—Inasmuch as this last apparatus constitutes, while not in actual use, a 
simple coupling to the clock shafts, it is not open to the objections to the ordinary 
means of producing this acceleration or retardation, when the motion is carried 
through several additional wheels and pinions.-] 
3 & 4. Clamping and slow motion in declination. The clamping by Hook’s 
joint handle; the slow motion by Hook’s joint handle, from a 
screw ground into a toothed sector of 18 ins. radius on declination 
clamp. 
5. Reading declination circle, sufficiently for finding purposes, by a long 
micro-telescope with right-angle prism on end. 
6 & 7. Arrangements for bringing into use the dark or bright field illumina¬ 
tions of micrometer as required. 
8 & 9. The regulation of both the intensity and the color of the illumination. 
The illumination arrangements, eye-end, and transparent position circle, method 
of working right ascension slow motion by bands, and accelerating and retarding 
mechanism, are all peculiar to the instrument, and applied for the first time. 
