1868. | Description of the Great Southern Telescope. 453 
iron lattice, and carrying the toothed 
sector (a) on their extremities. B is the 
clamp, which is a cast-iron halved ring, 
which runs on another portion of the polar 
axis, and to which it can be clamped by 
half a turn of the screw (b). This clamp 
is connected to the sector by the lattice 
arm and tangent motion ©, of a very 
peculiar construction. 
When the clamp is loose the instru- 
ment is quite free of all this apparatus; 
but the moment the clamp is tightened 
it becomes a portion of the polar axis; 
and, as it is connected to the sector by 
the tangent screw mentioned above, it 
serves to carry the telescope as the sector 
is moved by the clock. Again, small 
wheelwork and shafts being carried to 
a convenient position low down on the 
sector from the tangent screw, hook’s joint 
handles can be attached to each side, by 
which motion can be given by an observer 
looking into the telescope or finder, whe- 
ther the clock be in action or not. 
Quick motion in declination is obtained by a pinion working 
into a toothed wheel 4’ 6” diameter, bolted on the cube of the polar 
axis, from which a spindle is carried down to the end of the tube, 
where it is worked by a hand-wheel, accessible to a person looking 
into the telescope or finder. 
Slow motion in declination is obtained by a clamp 4' 6” 
diameter, and tangent screw, somewhat similar to the M, from 
which a shaft and hand-wheel is carried to make 7 also accessible 
to the observer. With such ease are all these motions worked, 
that two persons at the AX quick motion can reverse the instru- 
ment from east to west of its piers in three-quarters of a minute, 
and that with so little labour as to be compared by some to the 
working of a table microscope. It will be seen that, with the 
exception of the quick motion and clamping in AM, all the other 
operations are brought within reach of the observer himself while 
looking through either the large telescope or its finder, viz. slow 
motion AX, quick and slow motion declination, clamping decli- 
nation, and focussing; which last operation is performed by a large 
hhand-wheel, which surrounds the eye-piece, and round a portion of 
which the wire cords which come from the small mirror are wound. 
The support of the specula is one of the most important points 
in the mounting of the large reflector, and one which, if certain 
