100 
Description of a 
Without hoping that the one I am about to describe is 
free from every objection, I am disposed to regard it as 
more perfect than any one in present use ; and I would 
flatter myself, that the principles on which it is construct- 
ed, may, by experience, be so much improved upon, as 
to prove it really the important instrument of communica- 
tion the name implies. 
A cursory view of the accompanying engraving, will 
give a general idea of its formation, so as to render the 
description easily to be understood. 
This machine consists of a semicircle of any required 
magnitude, raised upon and firmly fixed to a strong w ood- 
en frame, four, six, or eight feet high, by means of iron 
rods or radii. To this frame is connected a strong up- 
right shaft of wood or iron, passing through the lower 
horizontal beam, and having attached at this part a per- 
forated shoulder, for the passage of the ropes from the 
machine to the observatory below. This shoulder is 
firmly fixed in the beam ; but is continued dow nwards a 
sufficient distance to rotate in a circular opening of the 
roof of the building, the shaft itself reaching to the bot- 
tom of the chamber, and is there received in a socket in 
which it plays. The object of this contrivance is, to per- 
mit the rotation of the telegraph without any obstruction 
to the free play of the ropes. The rotation, though in 
part effected by the shaft, is more especially dependant 
upon two or more strong iron castors, or rollers, sunk 
into the lower beam on each side the centre, and running 
on horizontal circles of iron let into the roof. The shaft 
preserves the machine in its proper situation. 
The frame is so constructed as to permit a strong iron 
cap to be fixed to the head of the shaft, w hich branches 
out into two arms, to form the centres, in which the axes 
of the wheels of the telegraph freely rotate. Of these 
axes, the one, interior and solid, passes through the other, 
