•_\SS \V. P. DOLLMAN ON A SIMPLE METHOD OF 



field used. I have had extra tubes made for my microscope (a 

 Van Heurck, by Watson), to take the place of the lower rack- 

 work tube and the upper sliding tube, which carry the photo- 

 lenses — the Dallmeyer at the bottom of the draw-tube, the Unar 

 (for which I had a new mount made, so as to get it inside the 

 tube) about 1| in. down the tube from the top, and the Goerz 

 outside on the eye-piece end of the microscope. These adapta- 

 tions enable the lenses to be carried at the suitable distances 

 from the object on the stage, and allow sufficient rackwork for 

 focussing. "When the distance is too great (as it will be in low- 

 power work) for the hand to reach the focussing pinion, I have 

 to use a Hook's joint focussing-rod ; but for the higher powers 

 I have a long rod on the right side of the camera, with a pulley- 

 wheel near the end, over which and the fine adjustment-screw 

 head runs a cotton-thread loop, which I find quite effective for 

 monocular work, even with a jV-in. objective. 



The camera I use is a whole-plate one with a long bellows, 



and, for long distance work, a telescopic attachment in front 



(made of rolled brown paper). The upright position of the plate 



in the camera is the more convenient for photographing opaque 



objects requiring to be lighted from the front and side, and, in 



this case, the objective should be divided horizontally. For 



transparent objects lighted centrally from the back the plate 



may be horizontal, and the lens divided vertically. I effect the 



reversal of the images on the plate, so that the prints will not 



require to be cut, and so simplify the mounting, by using a 



carrier in the dark slide (the whole-plate slide allows this to be 



done), in which the plate (5 by 4 in.) can be placed 2| in. out of 



centre, so as to receive the image from the right-hand or upper 



half of the lens on the left-hand or lower half of the plate. 



The opening in the carrier should be 7| by 4 in., a piece of glass 



2 j by 4 in. filling the otherwise unoccupied end. A screen of 



blackened card or thick paper with an aperture in the centre of 



2 1 by 3 in. should be placed in the carrier, to protect one-half of 



the plate while the other is being exposed. After exposing one side 



of the plate the slide is taken into the dark room, and the plate 



moved to the other end of the carrier. Then the screen on the 



objective is moved half round, or, in the case of a lens in the 



(haw-tube, the tube is given a semi-revolution without disturbing 



the focus, and the second exposure can be made. It is important 



