Machine for Microscopic Writing, 
61 
glass, which should just touch, but not be pressed against the 
diamond. Under the glass holder (3) is a weak spring (9) 
attached to a short arm (10), which is connected by a hinge with 
a little pillar (11) fixed to the upper stage {F) ; under this arm 
is another shorter but stronger spring (12), which, yielding to 
the action of any force depressing the arm (10), restores it to 
its place on the action of the force being discontinued. From 
the free extremity of this arm a wire (13) proceeds to the base 
of the stand, where it is fastened to a lever (14), which is at- 
tached to the lowest brass plate {E) by a hinge (15), which 
Fig. 4. 
allows of motion only in a vertical direction : when the end of 
this lever (14) is pressed down, it draws down the extremity 
of the arm (10), carrying the spring (9) which is then brought 
to act upon the glass holder (3), pressing the glass upward 
against the point of the diamond (^Z) ; a spring (16) under 
the lower lever (14) causes it to return to its position when 
the pressure is removed. Two screws (17, 18) pass through 
this lever, by means of which the extent of its movements, 
and consequently the pressure of the spring (9) under the glass 
holder (3) are regulated. One of these screws (18) serves to 
