101 
Revolving ^Telegraph, 
which is a cylindrical tube. Of the two wheels which 
work the shutters of the windows of the telegraph, the 
outer one is fixed to the solid axis, which, at the further 
extremity, where it passes out from the hollow axis, has a 
short upright, to which is attached a returning arm, running 
parallel with the axis, and having at the extremity one 
of the shutters dovetailed into it ; beneath this, a friction 
roller plays upon the periphery of the hollow axis, there- 
by supporting the weight of the shutter, and facilitating 
the motion. The inner wheel is connected to the edge 
of the hollow axis, and has the second shutter morticed 
firmly into its interior edge, so that it plays exterior to 
the first shutter, as closely as the parts will admit; and 
to prevent any interruption from each other, a narrow se- 
micircular rim along the edge of the telegraph may be 
adapted, to preserve each in its line of motion. 
These shutters are formed of thin well seasoned plank, 
sheathed with copper or tin plates, or the shoulders may 
be small iron rods, terminating in broad paddles of an 
appropriate form. The wheels which work them may 
be ot any size that experience shall direct, probably 
about one third in diameter, of that of the semicircle con- 
stituting the telegraph. 
The telegraph itself is formed of two parallel semicir- 
cular sheets of iron or copper, of six inches or a foot 
wide, situated about two, three, or four feet apart, (more 
or less, according to the size of the machine, and as ex- 
perience may approve,) and divided into thirteen equal 
chambers, all being accurately closed before and behind; 
an opening or window being cut in each chamber on both 
sides, of such a size as readily to be seen at the stations 
next adjoining, by the free passage of the light; a suf- 
ficient interval between each opening being preserved, to 
render the windows accurately defined: to make the 
bright appearance of the windows more conspicuous, eve- 
