2190 Journal of Applied Microscopy 



MetJwds of Pi-eparing Cheap La/iteru Slides. The photographing of objects 

 or photographic reproduction of drawing or cuts is always the'most satisfactory, 

 and any attempt to make slides in any other way is always more or less disap- 

 pointing. On the other hand, the illustrations desired for a particular lecture 

 may have no permanent value and and can be used only once, or at most a few 

 times. In such cases one does not feel warranted in going to the expense of 

 having a photographic slide made. Again, in a lantern lecture it is not possible 

 to use a blackboard, but it is desirable to indicate the spelling of terms, show 

 simple diagrams, etc. Hence, methods of preparing simple, inexpensive slides 

 may not be out of place, although they may be familiar to those who have had 

 experience in running a lantern. Where tables of figures are to be reproduced, 

 quotations made, etc., a stencil can be made on a typewriter and transferred to a 

 piece of plain glass in the same way that a mimeograph copy is made. Frequently 

 a fairly good slide may be made by moistening the glass plate with the tongue, 

 allowing it to dry, and then writing on it with ordinary writing fluid, and when 

 the ink is dry, rubbing lampblack over it with a piece of cotton batting. Or, 

 again, the glass slide may be blackened by holding it over a piece of burning 

 camphor until it is opaque, writing or drawing on it with some sharp pointed 

 instrument, as a needle, and then dipping it in a very thin shellac, which makes 

 the slide, if properly protected, quite permanent. The most satisfactory way, 

 however, is to coat the slide with some transparent substance, as shellac, Canada 

 balsam, or best of all, thin celloidin, and allow to thoroughly dry. In this case it 

 is possible to write on the glass with a fine pointed pen and India ink. Where 

 desirable, different colored inks may also be used. Shaded drawings may be 

 made on a ground glass slide with a lead pencil, then the slide afterwards ren- 

 dered transparent by running over it a coating of Canada balsam. 



In making photographic slides a great deal of good work, especially copying, 

 can be done with very simple apparatus. For example, a very satisfactory 

 camera for this purpose can be easily and cheaply made, using the projection 

 lens of the lantern for the lens of the camera, especially if this is a short focus 

 one. The body of the camera can be made of two boxes which slide into each 

 other, the lens being fitted into the closed end of one of the boxes and a plate 

 holder into the closed end of the other. Some of our best slides have been made 

 with a similar arrangement. Ordinarily the lantern slide is made for a negative 

 and is a positive. Frequently, however, a negative is quite as satisfactory. 

 Indeed, for tables and line drawings it is even more desirable. It looks more 

 like blackboard work and can be seen more distinctly in a rather light room 

 than the positive. It is also much cheaper. Where it is desired to have the 

 lines black on a light background it can be readily and cheaply secured by making 

 the drawings on the blackboard, photographing them, and using the negative for 

 a slide. This method has been used very successfully by Professor Schneider 

 of the North-western School of Pharmacy. It perhaps ought to be stated that 

 where the negative is to be used as a slide, the pyrogallic acid developer 

 can not be used, as it is liable to tint the slide. W. D. Frost. 



Bacteriological Laboratories, University of Wisconsin. 



