1885. ] Microscopy. j 217 
Varying the thickness of the sections —In Fig. 2 will be seen a 
milled head, f, which, when turned, controls the movement of 
the clicks which, acting upon the ratchet wheel attached to the 
micrometer screw, regulate the thickness of the sections. This 
may be done so as to allow the clicks to engage one-half, one or 
several teeth of the ratchet wheel as may be required. When 
arranged for one half tooth, the sections will be z>49; of an inch 
(.0025™") in thickness, when arranged to engage a whole tooth 
sooo Of an inch (.005™") and soon. At first it is well to use a 
whole tooth, as when thinner sections are cut so much depends 
on the sharpness of the razor. After cutting for some time the 
machine will suddenly stop, the object ceasing to rise when the 
handle is turned. This means that the full extent of the microm- 
eter screw has been reached. It is necessary then to turn the 
large milled head (Fig. 2 c) downwards, which will allow the car- 
riage containing the object to fall to its lowest limit. It will be 
, necessary now to raise the socket (Fig. 2 g) in which the object is 
held so as to be in position to come in contact with the razor. 
This milled head (Fig. 2c) is useful for rapidly getting the object 
in proper position and avoiding considerable loss of time in turn- 
ing the handle. The frame (Fig. 2) which holds the socket is 
arranged with two quadrants, so that the socket may be set at 
any angle desired, and may be clamped with the milled head 
underneath it. This is for use when the object has not been sym- 
metrically imbedded. The nut (Fig. 17) is for tightening up the 
spring which draws the carriage of the machine back after hav- 
ing been pulled forward. In case this does not work properly, it 
is only necessary to unloose the two screws and with some strong 
but blunt pieces of steel placed in the two holes, to rotate the nut 
so as to give a proper tension to the spiral spring. en this is 
done the screws should be tightened up again to keep the nut in 
place. 
The lock nuts (Figs. 1 and 2 s) should be screwed up suffi- 
ciently tight to barely prevent the carriage from falling by its own 
weight, so that when the milled head (Fig. 2 c) is screwed down 
a slight pressure with the finger is necessary to make the car- 
riage fall. 
To arrange the machine for cutting different sized blocks of 
material, it is only necessary to raise or lower the arm (Figs. I 
and 47). When this arm is in a vertical position the machine is 
arranged for its maximum traverse. When turned to the right 
and placed horizontally it is at its minimum traverse, The cord, 
however, must always be in the groove of the wheel, %. 
It is important to keep the strings which give motion to the 
endless band in proper position: The string (Fig. 1 /) should go 
from the end of the wire, m, round the groove, z, in the pulley 
and thence to the elastic band, 0. The elastic band, 0, should be 
stretched and placed over the hook attached to the arm, 7, care 
