MEDIUM-POWER PHOTO-MICROGRAPHY 



131 



With respect to the microscope : 



Personally, we have found that the microscope is best placed on a solid floor, the 

 limelight there too with the gas bottles in suitable position. The mirror (flat side 

 usuallj^) is protected from extreme light by a green glass, and the water-bath and 

 auxiliary condenser added. The mirror must be fidgetted about until the specimen, 

 whether one for high- or low-powers, is properly illuminated, the microscope of course 

 being quite upright. Here is the first difficulty. It is not easy to get the mirror in 

 situ when the microscope is out of its usual position ; too little room is often allowed 

 for the operator to apply his fingers to the delicate snbstage movemerits, especially 

 that of adjusting the diaphragm. Presuming this is accomplished, the wooden 

 apparatus is now placed over the microscope without touching it, which is not always 

 so easy as may be imagined. The union, which had better be by a velvet bag, is then 

 made between microscope and camera. The operator now is able to stand or gently 

 kneel whilst he completes his focussing. The light is cut off the mirror before 

 exposing, by the use of a large black card interposed between the light and the 

 mirror. It will be seen on consideration how very much more fatigue is entailed by 

 the use of this apparatus. In Dr. Van Heurck's design, Fig. 25, the camera is 

 kept fixed m situ over the microscope, and the operator puts his head inside it 

 through the door to primarily focus with, and is said to find it most comfortable ; 

 whilst to finish on the ground glass, he uses a stool. In Zeiss s last apparatus, 

 as will be seen by inspecting Figs. 26, 27, p. 57, it is easy to shift the camera 

 without much trouble. 



Whilst personally never using a vertical apparatus save when the natui-e of the 

 specimen demanded it, still we feel it incumbent to add that all the excellent work 

 done by Dr. Van Heurck and which in some instances has rarely ever been equalled 

 and never surpassed, was all done by his special form of upright camera and therefore 

 he very justly champions its cause, and challenges other workers to try it before using 

 the more ordinary horizontal apparatus which he has now discarded. One great 

 objection in the upright apparatus is that all high magnification must be obtained by 

 eye-piecing, and hence the use of camera "length" for that purpose is lost. 



We should add that we hear the upright apparatus sold by Baker, Beck, 

 Reichbert and Leitz, well spoken of by those w^ho should give us trustworthy 

 information. We understand too that lately our justly praised fellow- worker, Mr. 

 Pringle, has designed a still more elaborate upright arrangement and that it is made 

 by Messrs. Watson & Sons to his satisfaction. 



It is needless to add that the description given here when the apparatus is used 



