Forty-feet Refecting Telescope. 361 
poles as well as the large one, is carried round with four divi- 
sions. In order not to weaken the great pole by many holes, 
the braces secure it by a double iron strap, abed, fig. 14; and 
the small supporting poles which rest upon 19, 20, 21, and 22, 
fig. 2. are at the same time joined by a single screw-bolt, ef 
which passes through the loop g h i at the end of them, and 
through the straps which hold the braces to the great pole ; 
see fig. 1. 
The back of the ladders is bound together by a large cross, 
a b, c d, from the 10th flat to the middle braces, and by two 
horizontal pieces, ef, g h, as represented upon a small scale in 
fig. 15. The cross is bolted in twelve places to the ladders, 
and the horizontal pieces in six places each. The size of these 
braces is 6 inches by 4 ; but the lowest horizontal beam, which 
is used for a point of suspension to lift the mirror in and out 
of the tube, is 6 inches and a half by ; and the bolts that 
hold it to the ladders are also very .substantial. 
The front of the ladders, it is very evident, would admit of 
no brace, and is left entirely open for the tube of the telescope 
to range in. It receives, however, some confinement from the 
moveable gallery, which is always hung across the front, in 
the place where observations are to be made. 
This gallery is next to be described. It consists of three se- 
parate parts : two double side brackets with a small platform 
upon them, and a middle passage. The whole of it when 
joined together is properly railed in at the front by wooden 
palisades ; and on the inside by light iron-capped bars. Each 
of the brackets by which the gallery is supported consists of 
three frames ; a parallelogram for the bottom, with two trian- 
