62 
Machine for Microscopic Writing, 
limit the upward movement of the lever : this is effected by 
means of a moveable nut (19), above the arm, which can 
be placed in any required position; the other screw (17) is 
for regulating the pressure against the diamond ; it admits of 
its end (20) being fixed at such a distance from the brass plate 
(J5), as to allow of any required extent of depression of the 
lever : it is obvious that the more this is depressed, the lower 
does it draw down the arm (10), carrying the spring (9), and 
the stronger therefore is the pressure of the spring against the 
glass. By connecting a second lever with the sprinjj, and 
allowing one to be depressed more than the other, two different 
degrees of pressure against the glass may be secured, and the 
diamond may thus be made to give marks of different depth 
and thickness, so that writing may be produced with fine up- 
strokes and thick doim-strokes^ as in writing with a pen. 
It is unnecessary to do more than allude to the excellence 
of the work, and the perfect action of the mechanism. These 
are manifested by the fidelity with which the smallest move- 
ments are transmitted and recorded, every such movement, it 
will be remembered, having to be transmitted through three 
joints with two sliding-pieces ; each of these joints must 
admit of free and easy motion in every direction, while all 
tremor, or other movements than those directed by the will of 
the operator, must be precluded. How completely the 
object is accomplished is within the personal knowledge of 
many gentlemen present who have themselves had the oppor- 
tunity of testing the capabilities of the machine. Were other 
evidence necessary, reference could be made to the eminent 
President of this Society (Dr. Carpenter), who, on a first trial 
of the machine, produced an inscription of three lines in less 
than the 1 -10,000th of a square inch. Of this space the 
signature takes up not more than one-third, or less than 
l-30,000th of an inch ; the small letters of the writing are 
but 1 -1150th of an inch high; yet, notwithstanding its 
minuteness, the characteristic peculiarities of the autograph 
are unmistakable. 
The securing of a good diamond point is a matter of first 
importance : preference is given to a turned point, as a natural 
splinter, though it gives fine strokes, does not mark equally 
well in all directions. These points Mr. Peters prepares 
himself with the same skill and delicacy of touch shown in 
the construction of the other parts of the machine. 
In using the machine both hands have to be employed. 
While the right hand guides the pencil {X), the other is en- 
gaged in managing the lever (14) by which the action of the 
diamond is governed. Attention is necessary to insure the 
