10$ Description of a 
ry part of the machine maybe painted black,— the wheels, 
shutters, frame, and even the whole inferior semicircular 
space. 
The ropes that move the wheels, (by which the shut- 
ters are made to close the window required,) are carried 
down into the observatory by appropriate pulleys, and 
through openings in the lower beam and shoulder of the 
shaft. These ropes are divided accurately by spaces 
equal to the thirteenth part of the diameter of the wheels, 
and are to be numbered i, $, 3, % &e. corresponding with 
the thirteen chambers in such a way, that the two ropes 
which go to one wheel may have the order reversed, so 
that by bringing down a particular number of the rope 
to a fixed point on the shaft, we shall know the corres- 
ponding window above, is closed by the shutter, connect- 
ed with the wheel we are turning. The double number- 
ing of the ropes may, perhaps, be obviated, by attaching to 
one of them a weight sufficient to draw back the shutter to its 
point of departure ; in which ease, the shutter will always 
remain below the range of windows, unless the opposing 
rope is pulled by the observer, to the point desired. 
To employ this telegraph by night (which, however, is 
rarely requisite), lamps are placed within the chambers, 
and the intensity of the light hereby produced, is greatly 
augmented by lenses fitted to the windows. These might 
be fixed in a semicircular frame, which could be made to 
sink during the day below the range of windows. If 
used by night, four shutters must be employed (two on 
each side) to obstruct as necessary, the light from the ad- 
joining station on either side. 
Over the central window of the telegraph is fixed a 
sheet iron or copper parallelogram, or tower, six, eight, or 
ten feet high, of equal width with the machine. This is 
divided into three or more chambers, the lowest one 
blank, for the reception of blinds running in appropriate 
