4*2 
MR. BARLOW’S ACCOUNT OF THE CONSTRUCTION OF 
On the upper part of the same interior frame are fixed two cast-iron rollers, 
on which the bearing frame rests, serving to relieve the machine of the friction 
that would otherwise take place when the telescope is raised or lowered. The 
two iron rods seen on each side, turning in two eyes below and adjustable at 
top by nuts and screws, were intended to serve as braces and to preserve 
steadiness ; they are not, however, essential, as the instrument has every requi- 
site stability without them. 
Such is a general description of the stand ; the manner of working it will be 
understood from what follows. 
Below the fixed cross pieces, in the middle of the swinging frame, is a double 
fixed pulley, and to the lower part, on the inside of the sliding frame, is another 
double pulley, which rises and falls with the sliding frame. The end of the 
rope is fixed to the cross piece, descends and passes over one of the lower pul- 
leys, thence over one of the upper, again descends, passes over the other lower 
pulley, then over the upper pulley, thence again to another single fixed pulley 
on the diagonal brace ; it then passes over the lower barrel, which is turned 
by means of the wheel, pinion, and handle, shown in the plate. The power 
gained by the pulleys is 4 to 1, by the wheel and pinion 4 to 1, and by the 
barrel and handle 4 to 1, making in all 64 to 1. By these means the telescope 
may be raised even at its heaviest purchase with great facility. 
This part of the machinery, however, is only intended to bring the telescope 
to an approximate altitude ; after which, the part employed for bringing a star 
into the field, and for following it in altitude motion, is as follows. 
At the extreme end of the bearing frame is a fixed pulley: to the back of the 
sliding frame, another ; to the front of the same frame is another similar one ; 
and a fourth at the other end of the bearing frame. The rope is first made fast 
at the extreme end, then passes over the pulley at the back of the sliding frame, 
thence over the pulley at the extreme end ; whence it comes directly to the 
upper barrel ; and after a few turns about this barrel, passes to the pulley on 
the front of the sliding frame, and returning passes over the pulley in the 
bearing frame near the upright stancheon, then over a fixed pulley on the 
brace : to the end of the rope is attached an iron weight of fifty-six pounds, 
which passes through a hole in the floor and hangs suspended in a well-hole 
below, serving thus to take in the slack of the rope, thereby keeping it always 
tight on the barrel, and also serving as a counterpoise to the swinging frame 
