.1898.] " MICROSCOPICAL JOURT^AL 35 



microscope, and itts inner edge held firmly in contact with 

 the brass pillar supporting the stage and tube. Be care- 

 ful that both sides of the glass plate are parallel to the 

 middle diameter of the field of view; then lay on the 

 glass plate, a thin glass slip whose edge must be adjusted 

 so as to bisect the field of view longitudinally to the edge 

 of the slip after its edge has been focussed on by a l-6th 

 objective. Compress, and retain the slip in position. Care- 

 fully remove the stage, and by the aid of a small dia- 

 mond trace a line along the edge of the slip on the left 

 side of the stage plate. Or, a fine splinter of flint, or 

 carborundum will serve to scratch the line. If this is 

 done properly the line may be shoved through the field 

 for a full inch or more being continuously in view in a 

 field of 2-lOOths of an inch. This line once established 

 on the plate becomes a guage or recording point for all 

 objects on a cover glass mount of one inch area within 

 close limits. Additional benefit is derived from tracing 

 such a line on the rigid metal stage plate. The line 

 traced on themetal plate must, if prolonged, pass through 

 the center of the field of view, when limited to the field 

 of a I'-G objective. 



The same line also becomes a guage line, enabling the 

 field of any object to be recovered subsequently. In 

 order to utilize this line at its full value, it is necessary 

 to make an easily seen dot on the axis of the line at a 

 distance of one inch from the center of the field of view, 

 this line and its point is fixed on the left hand side of 

 the metal plate, being the equivalent of the fine line on 

 the glass plate when used above it. The index dot may be 

 fixed by a few trials, while the glass plate with its guage 

 line is in position on the metal stage. The dot should 

 register under the line at an inch from the center of the 

 objective. 



Assuming that these two guage lines have been proper- 

 ly traced on the glass and the stage plate, one can theii 



