328 Application of Photography to the Self-registration 
The cylinder consists of an ordinary French glass shade, black- 
ened on the inside, about fourteen and a half inches in cireumfer- 
ence and ten inches high. One end is closed by a metal cap pro- 
vided with a concentric axis, three inches long, a bent arm or 
crank is attached to the axis ei4 
by a set screw, and engages ; 
with a slit in the hour hand 
of the time piece, by which 
the whole is made to revoive. 
The weight of the cylinder is 
borne upon five friction rollers 
set in a light frame; two of 
er size at the opposite end{ , 
of the frame, are sufficiently © 
separated for the body of the 
cylinder to rest upon them, 
near its hemispherical eid ; 
the other is set horizontally, Cylinder and Copper case. _ 
and works against a small 
brass plate at the base of the axis; the whole should be carefully 
turned and truly pivoted. In the arrangement of the inventor, 
after placing the paper on the cylinder as here described, a secon 
cylinder very slightly larger is slipped over it, and retained in a 
concentric position, by pressure upon a few coils of tape wound 
round the capped end of the inner cylinder and kept wet; the 
object is to protect the paper aud keep it damp, for which pur- 
pose, also, a piece of wet lint is placed between the cylinders 
at the point. An accident to the external cylinder led to the 
adoption of a different plan at Toronto, which has been found so 
convenient that the former one has not been reverted to. 
fore darker; the paper may be applied, and removed with great 
expedition, and without exposure to stains from contact with 
