THE BOOK OF THE LANTEKN. 105 



the necessary exposure ; but in this case care must be 

 taken that the plate is thoroughly well drained, for a drop 

 of the silver bath solution, if allowed to get into actual 

 contact with the negative, will inevitably spoil it. 



But those who advocate the wet process for lantern- 

 slide work nearly always work from larger negatives 

 with the camera, and by following the directions now 

 given it will be found that very good results can be 

 obtained. 



Place the negative to be copied in a suitable frame 

 against the window. This can be done by fixing an ordi- 

 nary printing frame (with the spring removed) against 

 the glass, and by covering up the rest of the window- 

 panes with brown paper, or some other opaque material. 

 Then support the camera on a stand or table, exactly op- 

 posite the negative, taking care that it is square with the 

 negative and carefully focus the image on the ground glass. 

 A focussing glass is a very great help in this work, for the 

 image is often so dimly illuminated that it is difficult to 

 ascertain whether it is sufficiently sharp or not. With 

 regard to exposure, it is very difficult, in fact impossible, to 

 lay down any hard-and-fast line. I can only say that 

 with a negative of normal density and with a favourable 

 light, the exposure should be about one minute ; but it is 

 of course governed by the type of lens used, and the par- 

 ticular stop employed with that lens. With a portable 

 symmetrical of 5 -inch focus and using No. 4 stop, the 

 exposure with a normal negative will be about that which 

 I have indicated. 



But the great thing which ensures success in this process 



