58 
Machine for Microscopic Writing. 
end (^K) to the brass plate (Z>) by two concentric rings (X M) 
in the way already described ; the upper portion i^G) remains 
attached to the upper stage (i^) as at first, but is shortened by 
cutting off apiece from its lower end (^N) : into the space thus 
caused between the two parts (iV K) of the original rod, there 
is introduced' a piece composed of two short rods (P O and 
O Q), united by a universal joint (O), similar to those by 
which the two portions of the vertical rod are connected with 
the two stages. Each of the free ends (P and Q) of this 
jointed member is made to slide truly and smoothly in bear- 
ings supplied to the cut ends (jfiT and iV) of the divided rod, 
so that the position of the joint (O)may be varied at will: its 
place having been determined, it is fixed by means of a screw 
(i^), the end of which is made to press against one of the 
sliding-pieces (O Q) ; and now, instead of a single lever con- 
sisting of a simple vertical rod {G fig. 1), there are two 
levers {GO and O H, fig. 2) united by a moveable joint (O). 
The first lever, extending from the base of the stand to the 
joint, has all that portion below the pivots on which it is sus- 
pended for its long arm {IC H)y while its short arm (jfiT O) 
extends from the same pivots to the joint (O), and varies there- 
fore in length, which is determined by the position of the 
joint. The second lever, extending from the joint (O) to the 
upper end of the combination has for its short arm all 
above the pivots connecting it with the upper stage ; its long 
arm {G O) consists of the portion between the same pivots 
and the moveable joint (O), the position of which determines 
the length of that arm. Thus it is seen that the short arm of 
the first lever (K O) and the long arm of the second one ( O G\ 
vary in length with different positions of the moveable joint, 
while the effect of their altered relations is always in the same 
direction. 
With this combination, any movements of the lower end of 
the rod fig. 2) are repeated, the direction reversed, and the 
extent diminished, at the end of the short arm of the first 
lever ( O), that is at the joint ; the motion is there transferred 
to the long arm of the second lever, at the end of the short 
arm of which {Z )^ the direction is again changed, and the ex- 
tent a second time diminished. 
The amount of diminution which the machine is capable of 
effecting, ranges from 110 to 6,250 times linear: these limits 
are determined by actual trial ; thus, if a square be drawn, the 
sides of which are 5 inches long, the length may be reduced 
to the 122-nd of an inch, that is 110 times, or it may be dimi- 
nished to 1-1 250th of an inch, or 6-250 times. An arrange- 
ment of the leverS; such that the arms are in the ratio of 12 : i 
