382 Dr. Herschei/s Description of a 
answer the purpose of viewing, pretty minutely, every object 
that passes the meridian. 
Before I can give the particulars of this side motion, some 
other things must be explained. The point of support rests in 
a pivot ; but this alone could not have given steadiness to a 
tube of 4 feet 10 inches in diameter, loaded with the weight 
of the strengthening bars, and speculum, which rest upon it. 
Two moveable supporters have therefore been provided at pq> 
fig. 34. They consist of two solid brass rollers, 3 inches thick, 
and 4 y in diameter ; set in strong frames firmly united to the 
sides of the tube, and resting upon the flat face of the square 
axle AB, which carries the pivot in the centre. The middle 
of these rollers is applied about 2 feet 2 inches from the centre 
of the pivot ; and being set so as to lose none of the motion 
which they may have upon the axle, we find that there is room 
for full as much angular motion of the rollers upon the axle, 
as there is for the tube between the sides of the ladders ; and 
indeed more than can be wanted, as 10 minutes of time are 
generally sufficient for viewing any object. 
The method of observing with this telescope is by what I 
have called the front view ; and the size of the instrument 
being such as would permit its being loaded with a seat, there 
is a very convenient one fixed to the end of it. The foot- 
board or floor, is 3 feet broad, and 2 feet 2^- inches deep. 
The seat is moveable from the height of 1 foot 7 inches to 2 
feet 7 inches, not so much for the accommodation of different 
observers, as for the alteration which is required at different 
altitudes, and which amounts to nearly 12 inches. One half of 
the seat falls down, to open an entrance at the back ; and being 
