208 THE PHOTO-MICROGRAPHY OF 



and secured upon a stout, smooth board, resting on a firm table 

 near the window. Fasten the camera-bed to one end of the 

 board. In front of it ]3lace the microscope screwed upon a block 

 of sufficient height to bring the tube opposite to the centre of the 

 camera-lens aperture, leaving a few inches of space intervening, in 

 order to permit of focussing the objective up and down, or rather 

 backward and forward, as the microscope tube is now horizontal. 

 The intervening space referred to may be bridged over by a sleeve 

 of black velvet, or anything pliable, which is at the same time 

 opaque and has a non-reflecting surface. The wrist end of a lady's 

 black undressed kid wousgnetatre glove, turned wrong side out, 

 will answer very well by tacking the larger end around the camera- 

 lens aperture, and securing the other end around the tube by 

 means of an elastic band. 



Next comes the condenser, which must be fastened to the end 

 of a tube which slides smoothly in a collar fitted around a hole 

 cut in the window shutter. By this arrangement the condenser 

 may be moved back or forth as circumstances require without 

 throwing it out of line. The position of the hole should be care- 

 fully regulated, so that the optical axis of the condenser will be in 

 the same line with the optical axis of the objective. 



The heliostat is placed outside of the window, either on a 

 separate shelf or on the end of the same board which carries the 

 rest of the apparatus, in which case the shutter with the condenser 

 must be notched at the bottom to fit over the board, and lifted 

 out while it is being pushed out of the window to a sufficient dis- 

 tance. When once regulated for the latitude and the time of day, 

 the heliostat moves by clockwork and requires no further attention. 



If artificial light is used, it should be enclosed in something to 

 prevent the rays from being diffused in the room. [When using 

 my kerosene lamp, I had a piece of stove-pipe in which a hole had 

 been cut opposite the flame for inserting the tube of the conden- 

 ser.] Having arranged all carefully in line, adjust the condenser 

 so that its focus will pretty nearly coincide with the focus of the 

 objective, or until tlie cone of light upon the object and the field 

 of the objective are of about the same size, and test the apparatus 

 with some slide re<|uiring fine definition and a low power. Focus 

 down with the coarse adjustment until the usual working distance 



