EJ 
60 MICROSCOPY. 
more in any direction, so that the object can be brought into the 
field of view; ais a glass plate held in place by the two pieces 
of wood with screws on the right and left; bis the wooden base 
of the affair with an oval opening for the illuminating apparatus 
to come up; this wooden base being covered on the inner or upper 
side with velvet to make smooth the friction on the under side of 
the stage. For use with a mechanical stage this arrangement is 
modified and much simplified, the large glass plate being merely 
attached to the stage, whose screw movements enable the object 
to be brought into the field of view. On the middle of the upper 
side of the glass plate are cemented four strips of glass as shown, 
just far enough apart to take in a common glass slide which is held 
in place by a couple of wedges of common sheet brass ; and on the 
middle of a slide is fastened the object to be cut, either with gum 
Fig. 41. 
arabic or sometimes with collodion. For holding hard objects like 
wood the arrangements are not ue quite perfected, but no special 
difficulty is expected. 
Fig. 42 gives a perspective view of the triangular wooden frame 
that holds a razor blade, r, whose edge and back come down lower 
than the rest of the frame. By means of the three screws with 
graduated heads the whole frame, razor and all, is raised or low- _ 
ered from the glass plate (a, Fig. 41) on which the triangle rests 
_ and slides with these three screws as its feet. ‘These three sup- — 
porting screws are cut with a thread that counts forty to the inch; 
the screw head is divided into one hundred equal parts, and can be 
_ moved without much difficulty through half of one division, a 
~ a vertical motion of s;4,5 inch to the cutting edge. 4 
