THE BOOK OF THE LANTERN. 217 



darkened to a small extent, fix and wash in the usual 

 manner, and then bleach it in a solution of mercuric 

 chloride. The result will be a plate covered with an 

 exquisitely fine translucent surface, upon which the 

 finest details will be visible. The exact amount of 

 exposure and development to secure this end may not 

 be at first hit upon, but one or two trials will be sure to 

 end in a satisfactory result. Some workers prefer to use 

 a plain glass upon which fine lines have been ruled 

 with a writing diamond. In any case the worker will 

 find the advantage of supplementing his eyesight, how- 

 ever good, by a focussing glass. In this way a far sharper 

 focus is obtainable than by the unaided eye. 



To describe the rest of the diagram, let me point out 

 that / is an ordinary microscopic paraffin lamp, furnished 

 with a reflector f, and that h is a condensing lens, having 

 attached to it a diaphragm-plate, e. 



Mr. T. Charters White, M.R.C.S., has published a 

 method by which photo -micrographs can be produced 

 without the aid of either a camera or a microscope, which 

 is very creditable to his ingenuity. I had recently the 

 pleasure of hearing him 'describe the instrument, while 

 he practically demonstrated how effectually it would 

 work. The apparatus was home-made, and such as 

 could be produced by any one with the minimum of out- 

 side help, although there are many accustomed to the use 

 of tools who could easily make it without any help at all. 

 I append a diagram which shows the various parts of this 

 simple contrivance (see fig. 54). 



It consists in a lidless box sufficiently large to con- 



