NOTES AND MEMORANDA. 



183 



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 arabic or sometimes with collodion. For 

 holding hard objects like wood the arrangements are not yet 

 quite perfected, but no special difl[iculty is expected. 



Fig. 2 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 cr loAvered from the glass plate (a, Fig. 1) on 

 which the triangle rests and slides with these three screws as 

 its feet. These three supporting 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, giving a vertical 

 motion of ^vo-o ii^ch to the cutting edge. 



Fig. 3 is a large view of one of the screws, with its indi- 

 cator. The indicator may be a simple pin set in the wooden 

 frame, but is more convenient if made movable around the 

 axis of the screws, so that when the razor is returned after 

 sharpening they may be all turned around to the of their 



Fig. 2. 





Fia. 3. 



.<r^TiT>- 



respective screws, and therefore all read alike, while the 

 successive cuts are being made. On the side of the indicators 

 are scales which show how many complete revolutions of the 



