1882.] 



MICKOSCOPICAL JOUKNAL. 



89 



of the body-tube just entering the 

 small circular opening of the camera. 

 A cone of opaque cloth is usually ar- 

 ranged about this opening to exclude 

 extraneous light ; but I have adopted 

 a different plan, because it so 

 happens that the bellows of my 

 camera-box is long enough to give 

 me all the range in magnification 

 that I desire. The opening in the 

 camera-front is about the same size 

 as the end of my microscope-tube. 

 Removing the draw-tube, I line the 

 main tube with black cloth, to prevent 

 reflection of light from the inside of 

 the tube, which would make it impos- 

 sible to secure a sharp definition, and 

 then fit in the eye-piece by wrapping 

 it with a strip of blotting paper. Over 

 this I slip a card having a hole in the 

 centre, and then, inserting the ocular, 

 I place the microscope in position 

 where the card, fitting against the 

 front of the camera, completely ex- 

 cludes any diffused light. 



In case I should, at any time, find 

 it desirable to increase the magnify- 

 ing power of my apparatus, I would 

 cut a larger opening in the camera- 

 front, and attach a hollow cone of the 

 requisite length to connect the mi- 

 croscope and the camera. The cone 

 might be of sheet-brass or tin, black- 

 ened inside, but one in every respect 

 as good, and much lighter, can be 

 made of paper in this way : After the 

 proper dimensions of the cone are 

 determined, take some writing paper, 

 and paste upon one side of it a strip 

 of black cloth — farmer's satin is very 

 good. Then cover the back of the 

 paper with paste, and roll up the 

 cone, the cloth lining being inside. 

 Three thicknesses of paper will make 

 it quite stiff. I use the same plan in 

 lining my microscope tube, and you 

 can see what a serviceable tube can 

 be made in this way. Beyond the 

 microscope are two ordinary con- 

 densers — the one nearest the source 

 of light, which is a student's lamp, is 

 a bull's-eye lens ; the other a small, 

 double-convex lens. Two condensers 

 are used, because a brighter illumina- 



tion of the object can thus be ob- 

 tained. 



At the back of the camera is a 

 plate of ground glass, upon which the 

 image from the microscope is re- 

 ceived. The image is focussed care- 

 fully upon this plate, by means of a 

 simple lens ; or, by what is still better, 



Fig. 31. 



a photographer's focussing-glass (fig. 

 31). It is essential to the success of the 

 operation that the image be carefully 

 focussed ; and when very delicate 

 structures are to be photographed it 

 may be desirable to use a plate of 

 clear glass instead of the ground 

 glass. When the clear glass is used 

 the lens of the focussing-glass must 

 be adjusted so as to focus upon the 

 inner surface of the glass, and then 

 the image is made distinct by turning 

 the fine-adjustment of the microscope. 

 A so-called "bank-note detector" 

 is also excellent for this purpose. 

 Before attempting to use the appara- 

 tus, it is necessary to adjust the mi- 

 croscope so that the optical axis shall 

 be perpendicular to the plane of the 

 ground glass. This adjustment is 

 best made at night, in the following 

 manner : A perfectly flat object, 

 such as a section of wood, is placed 

 on the stage of the microscope, and 

 the image on the ground glass is care- 

 fully examined. The microscope is 

 then moved about, if necessary, until 

 the image is as perfect as possible on 

 every part of the ground glass. When 

 this is done the stand should be fixed 

 in its place by cleats, so that it can 

 be replaced in position at any mo- 

 ment. Then the light and the con- 

 densers should be adjusted for the 

 best effect, and the proper positions 

 for the former marked on the base- 

 board. To adjust the light, remove 

 the ground glass, the ocular, and the 

 objective ; and, placing the eye so as 



