2284 



Journal of Applied Microscopy 



Fig. 2. — Copied ^ size from book with -|- o 

 supplemental spectacle lens and Bullseye 

 kodak. 



distances of from eight inches to sixteen inches from the camera, raising the ring 

 of the retort stand one inch each time. I then developed the film and found 



that the extreme pictures were deficient 

 in definition, but that from 10 to 14 

 inches they were quite sharp, and I have 

 made excellent lantern slides from them. 

 Moreover, as the size of the copy varies 

 with the distance of lens from object, 

 the fact may be usefully employed where 

 variation from the half size is desirable. 

 So satisfactory has this method turned 

 out that I have discarded my copying 

 frame and anastigmat, and I have just 

 made seventy excellent slides from neg- 

 atives so produced. Now let me shortly 

 describe the technique. To any fixed 

 focus hand camera carrying a 3i-inch 

 film or thereabouts, attach a supplemental spectacle lens mounted in a cap to fit 

 over the original lens. Ascertain by trial the distance at which the combination 

 gives a sharp focus with a large stop. In the case of a Bullseye kodak or any 

 other camera carrying a five-inch lens, this is a 13-inch spectacle lens — and 



the correct distance is 12 inches for a half reduc- 

 tion, or a Scinch lens at 4| inches for same size. 

 For use put on the supplemental lens, stop down 

 to smallest diaphragm,* and place camera over 

 book at any distance between 10 and 14 inches. 

 The book should be flat on the table and the 

 camera can be maintained in position by a pile of 

 books on either 

 side, or, as I pre- 

 fer, by a simple 

 little stand I have 

 devised therefor. 

 Exposure is best 

 effected by burn- 

 ing eight inches 

 of magnesium 

 ribbon above the 

 book by the side 

 of the camera. 

 Diffused daylight 

 in a room requires 

 about two min- 

 utes. The advantages of this method of working lie in the extreme simplicity of 

 the apparatus ; its portability enabling copies to be made in libraries, etc.; the 

 ease with which a book lying open is kept flat; the elimination of focussing, 

 with its loss of time; and the rapidity with which films may be changed as com- 

 pared with plates. Its disadvantages I have yet to discover. 



I might mention that this great depth of focus makes it equally valuable in 

 making negatives of small solid objects, beetles, geological specimens, etc. 

 College of Physicians and Surgeons, San Francisco. H. D'ArcY Power. 



* The smallest stop on a kodak is no longer small when the focus is reduced by the addi- 

 tion of a supplemental lens. This is easily corrected by placing a piece of cardboard in front of 

 the lens with the necessary perforation ; in the case of the full sized reproduction, about J^-inch. 



Fig. 3. — Fasciola hepatica, nat- 

 ural size, viewed from ventral 

 surface. Copied full size 

 from book with Bullseye 

 kodak and -j- 7 spectacle lens 

 at 4'i inches. 



Fig. 4. — Cysticercus cellulosae in the 

 human brain. Copied ^-size from 

 book with Bullseye kodak and -)- 3 

 spectacle lens. 



