436 Prof. Wa.uacr on the Invention of the Pantograph, 
working. Fig. 3. shews the copying point, and its apparatus ; 
P P is a black lead pencil, ¢¢ a tubular case into which the pen- 
cil is fitted tightly : these, when the instrument is not used, are 
detached from the arm and kept apart. The pencil-case has a 
flanch yy, which surrounds it like a collar ; the part ¢ of the case 
above the flanch, may be called its neck: W, W, W, are round 
discs of metal (three are shewn in the figure) ; each has a hole in 
it, through which the neck of the pencil-case may be passed ; one 
or more of these are placed on the neck when the instrument is 
used, they serve by their weight to bring down the copying 
point when raised in working, and also to give the proper degree 
of shade to the pencil line traced on the paper. There is a bent 
LEVER #2, the arms of which are nearly perpendicular to each 
other. It is supported at its angle by the fulcrum s, which 
stands on the arm of the instrument. The use of the lever is to 
raise the copying point from the paper by lifting the pencil- 
case in the tube T. For this purpose, there is a silk line 
Imn H, Fig. 1. (of which 7m, Fig. 3, is a part), fixed to it at /; 
this passes over the wheels of two small pulleys, one, m, support- 
ed on the beam over the centre of the wheel, Fig. 1, and another, 
n, fixed to the socket c, over its centre. The end H of the silk 
line is held in the operator's left hand while he works ; by draw- 
ing it he turns the lever about its centre. By this angular mo- 
tion, the arm under the flanch raises the pencil in the tube ; by 
slackening the line he allows it to descend, until its point again 
reaches the paper. 
The pencil-case, when it is put into the tube T, does not 
come into absolute contact with its inside, but is held firmly in 
an upright position, by pressure on the convex surfaces of five 
friction rollers which enter the tube, and project a little beyond 
its inner surface. ‘Two of these are at the top of the tube and 
two at its bottom, directly under the former (only one of each 
pair, viz. 7” 7’, are seen in the figure) ; the fifth, 7, is on the op- 
posite side of the tube, towards the wheel, so that its pressure 
may be opposed to that resulting from the combined pressure of 
