146 PRACTICAL PHOTO-MICROGRAPHY. 



Reduction or copying in the camera may be performed 

 most conveniently by the same arrangement as is figured No. 

 33 in our last chapter. The negative is placed in the " dark 

 slide " of the large camera ; distance is arranged by the rack 

 and pinion of the large camera, centering by its front motions, 

 while the lantern plate is held in the dark slide of the 

 smaller camera with the rack of which, by aid of an eye- 

 piece, focusing is performed in the usual way. The back of 

 the large camera bearing the negative may be pointed at the 

 sky, may be lighted by an angled mat white reflector, or may 

 have a sheet of ground glass or tissue paper placed parallel 

 with the negative and a few inches behind it. No light should 

 get past the edges of the negative into the large camera, but 

 this though a good precaution is not absolutely essential. 



A still simpler mechanism consists in placing the negative 

 against the pane of a window, lighting the negative either by 

 a reflector or by the sky, and photographing it to the slide size 

 in an ordinary camera. The day light enlarging apparatus 

 figured 32 in last chapter may very easily be utilized for our 

 present purpose, by simply fixing the negative in the window, 

 turning the camera round, and suppressing the easel. The 

 lens used must be rectilinear and may have a focus of 3 \ inches 

 or upwards. The author uses a " Rectilinear Stereo " lens of 

 about 3 inches focus. 



THE WET COLLODION PROCESS FOR SLIDES. 



In most books of photographic instructions that have any 

 pretension to completeness, an account of the wet collodion 

 process will be found. In " Processes of Pure Photography " 

 the subject is treated with sufficient care to enable any one 

 referring to that book to work out the process for himself, and 

 to succeed with the process for our present purpose. We pro- 

 pose here merely to accentuate, as it were, certain directions 

 given in the book alluded to. 



Though a lantern-slide is only three and one-quarter inches 

 square, it will be found almost necessary to use a larger plate 

 with the wet process, and to cut it down after the slide is fin- 

 ished. Five inches by four will be a suitable size. The glass 



