400 Dr. Herschel j s Description of a 
upon its end, which must have a screw upon it. The arbor 
which carries the dial-plate is then to be pinned fast upon the 
axle, and an adjustable hand being put upon the projecting 
arbor, a collet is slipped over it, and the milled nut screws it 
down, in any position that is to be given to it. 
The adjustable hand is made of a piece of springy iron, or 
steel, formed as represented at ik; but broader than clock hands 
usually are. It must have a pretty large circle in the middle,, 
with a hole wide enough to go upon the plate-arbor. The end 
k of the hand must project beyond the dial-plate a little way, 
so as to permit two screws, m n , to pass by it into a brass plate, 
with a small piece between, to allow some motion up and down 
to the hand. The plate which is fixed to the hand by the 
screws m n, returns under the dial-plate sufficiently to carry 
three pins that are to lift the lever b, when they come to the 
proper situation, in the same manner as those on the barrel 
lift the lever c. The dial-plate, close to the margin, should 
have as many small holes, to receive a pin, as there are num- 
bers marked upon it ; and in the hand, answering to the holes, 
must be fixed a steady pin to fall into any one of them, when 
the hand comes to be placed over it. There must be a small 
handle near the end / of the hand, by which it may be lifted 
up, and mcved into any situation that shall be required ; and 
care must be taken to have both ends properly counterpoised. 
In order to set the zone-piece to the breadth of any parti- 
cular sweep, as for instance two degrees, we make the work- 
man begin at the striking of the top bell, and while he turns 
the handle till the quadrant or polar distance-piece points out 
a change of two degrees, we keep the hand of the zone-clock 
lifted up, that the pin may be out of the holes upon the dial-. 
