66 



LABORATORY MICROSCOPES 



{_CH. 



\ 125. Marker for Preparations. (Figs. 61-66). This instrument consists of an 

 objective-like attachment which may be screwed into the nose-piece of the micro- 

 scope. It bears on its lower end (Figs. 61-3) a small brush and the brush can be 

 made more or less eccentric and can be rotated, thus making a larger or smaller 

 circle. In using the marker the brush is dipped in colored shellac or other cement 

 and when the part of the preparation to be marked is found and put exactly in the 

 middle of the field the objective is turned aside and the marker turned into posi- 

 tion. The brush is brought carefully in contact with the cover-glass and rotated. 

 This will make a delicate ring of the colored cement around the object. Within 

 this very small area the desired object can be easily found on any microscope. 

 The brush of the marker should be cleaned with 95% alcohol after it is used. 

 (Proc. Amer. Micr. Soc., 1894, pp. 112-118). 



61. 



62. 



63- 



FIGS. 61-63. Sectional Views of the two Forms of the Marker. 



FIG. 61. The simplest form of marker. It consists of the part SS with the 

 milled edge (M}. This part bears the society or objective screw for attaching the 

 marker to the microscope. R. Rotating part of the marker. This bears the eccen- 

 tric brush (B} at its lower end. The brush is on a wire ( W). This wire is eccen- 

 tric, and may be made more or less so by bending the wire. The central dotted 

 line coincides with the axis of the microscope. The revolving part is connected 

 with the ''Society Screw" by the small screw (S }. 



FIG. 62. 61S, R, and B. All parts same as with Fig. 6s, except that the brush 

 is carried by a sliding cylinder the end view being indicated in Fig. <5j. 



