452 Description of the Great Southern Telescope. [ Oct., 
of the polar pier, exert a certain force upon it in a direction at right 
angles to the polar axis. The direction of the force is independent 
of, and does not vary with, the turning of the polar ais, but is 
constant as respects any vertical line; therefore by applying a suf- 
ficient weight to the lever, the whole of the force R (Fig. 2) can be 
raised on this apparatus and so got rid of. When the instrument 
is on the meridian, either of the pairs of rollers aa’ (Fig. 3) is 
bearing the whole of this R, according to whether it be east or west 
of the piers: in a position six hours off the meridian the internal 
rollers ee’ are bearing all this; while in any intermediate position 
the weight is divided between ee’ and either of the pairs a or @. 
It should be remembered that in this instrument the counterpoise 
of the telescope is hung on the declination axis itself, consequently 
both the polar and declination axes are balanced inter se round 
their point of intersection, which is very much preferable to the 
too common mode of hanging the counterpoise to an extension of 
the polar axis; in which case both axes are out of balance, and this 
apparatus could not be effectively used. 
Having now got rid of the force R, the remainder, P, is easily 
disposed of. There are two large frames carrying two rollers 
each, one placed between the large bearing of the polar axis and 
the cradle, and the other outside the smaller bearing. These are 
connected by levers running along the side of the cube of the polar 
axis, where they are centred; and it is so arranged, that by screw- 
ing up a nut which connects the levers to the frames, the whole or 
any portion of the weight of the declination axis can be raised out 
of its Ys in a direction parallel to the polar axis P (Fig. 2), while 
the apparatus mentioned above relieves the remainder R (Fig. 2). 
The combination of these systems gives a wonderful ease of 
motion, combined with: perfect steadiness. Fig. 5 shows the appa- 
ratus in situ in the polar axis. 
Hand Motions.—There are four separate gearings for these, viz. 
quick motion in right ascension (At); slow motion ditto (AX); 
quick motion in declination (D); and slow motion in declina- 
tion (D). 
Quick Motion AX is obtained by a pinion working into a 
toothed wheel on the polar axis, immediately below the cube, 
from which a shaft is brought down, connected by bevel wheels 
to another running through the equatorial pier, with a wheel at 
each side, to which motion can be given by a person while watching 
the A circles. 
Slow Motion A is obtained by a differential motion between 
the clock-work sector and AM clamp, see Fig. 6, where A is the 
sector made up of a cast-iron foundation piece, bored accurately to 
fit a portion of the polar axis, on which it is strung, but not made 
fast. From this branch two tubes of steel, trussed with cast- 
