Forty-feet Reflecting Telescope. 385 
A micrometer-motion to perform the sweeps. 
A zone-piece, to point out the required limits of the in- 
tended zones. 
A small apartment to inclose these motions, and the candle 
which is required for the workman. 
And a ready communication, for the observer to direct the 
workman in the required motions. 
All these conveniences were gradually brought to perfection 
with iny 20-feet telescope ; but here, they were at once, and 
with great advantage, designed and executed in their most 
improved state. 
A' B' C' D', fig. 3. is the floor of the observatory, 8 feet 5 
inches by 5 feet 5. It is of a proper height, and has a double 
window towards the west, with a shutter to be used at night. 
Fig. 1. gives a sufficient view of it. 
E' F' G' H', is the floor of the working room, which is 
6 feet 6 by 4 feet 5 ; and has two small windows, one to the 
south, the other to the east. Its height is considerably less 
than that of the observatory ; and a view of this may also be 
seen in fig. 1. 
The distance between the observatory and the end of the 
telescope, is evidently too far for a conversation in the open 
air, between the observer and assistant ; especially as the 
latter, on account of his candles, must be inclosed : and ought 
not to leave his post at the time-piece and writing-desk. Add 
to this, that when the observer is elevated 30 or 40 feet above 
the assistant, a moderate breeze will carry away the sound of 
his voice very forcibly. A speaking-pipe was therefore neces- 
sary, to convey the communications of the observer to their 
destination. 
