1868. | Description of the Great Southern Telescope. 451 
with respect to the axis as it turns, but is constant as regards any 
vertical line. Now if KR could be disposed of, it is evident that the 
case would be that of an equatorial at the pole of the earth, all 
the pressure being in a direction parallel to the polar axis. This, 
then, could be readily relieved by anti-frictional apparatus. To 
understand how this Kis disposed of, refer to Figs. 3, 4, and 5. 
Fia. 3. 
Fig. 3 shows the apparatus, by which this is accomplished, 
taken asunder. It consists of two nearly semicircular cast-steel 
rings, A and B, very strong, between the Jaws of which, when to- 
gether, are held the gun-metal carriages, shown at E FE’, carrying 
three rollers each, one pair each, aa’ (one only of each pair can be 
seen in the figure), and one single, ee’, at right angles to the other 
two. ‘This apparatus when bolted together embraces the declina- 
tion axis where its axis crosses that of the polar axis (where the 
declination axis is formed as at Fig. 4). The two pairs of rollers 
aa’ (Fig. 3) work on the rings A A’ (Fig. 4), whilst the third 
rollers ee’ (Fig. 3) work in the groove B (Fig. 4). The lower 
half-ring has a steel pin d (Fig. 3), which rests in a cavity prepared 
for it at the bottom of the polar axis, where it forms the fulcrum of 
the lever, while the upper half-ring is prolonged into a stiff trussed 
bar which runs up through the polar axis and projects at the upper 
end, where it is acted upon by a sector and lever, which by the 
application of sufficient weights, which hang down the eastern side 
