WILLIAM B. DWIGHT. WL 
For the present machine for rock-slicing, the following 
powers are claimed, possessed, it is believed, by no other 
machine of the kind: 
1. Great facility in grasping or clamping with firmness 
Specimens of every variety of size and shape with very 
little expenditure of time. 
2. A high degree of precision, and yet of rapidity of 
adjustment of the desired plane of section to the plane 
of the cutting disc. 
3. An absolute control over the level of the large and 
thin cutting disc, which should be eight inches or more 
in diameter and as thin as ordinary tin plate. This con- 
trol compels it, however warped, to cut a perfectly true 
plane, in large specimens of several square inches. 
4. Capacity, by reason of the above arrangements, to 
cut sections of several square inches in such a degree of 
thinness that very little subsequent grinding is required. 
It would be impossible, without a large number of il- 
lustrations and a lengthy description, to give any ade- 
quate idea of the details of the mechanism. The follow- 
ing very general description will suffice to indicate the 
character of the adjustments and the methods of control : 
Upon the bed of a strong lathe, a large cast iron table 
is firmly bolted ; the surface of this table is machine- 
planed to a true level. Upon the front left-hand corner 
of this table (¢. e., left hand of the operator), is bolted 
the standard-frame carrying the standard vertical bar 
turning uponcenters. <A stout cylindical horizontal bar, 
carrying the jaws, has a vertical motion upon this stand- 
ard bar, adjustable by a long vertical screw, while it also 
has a horizontal motion by the turning of the standard 
‘upon its centers. This general arrangement of the 
standard and horizontal bars formed the basis of the 
original device of Professor Hall. 
The jaws have a regulated movement along the hori- 
zontal bar, and at the same time a rotary movement by 
@al 
