230 THE BOOK OF THE LANTERN. 



open, like a sleeve, for the reception of a slip of paper, 

 like that shown in fig. 58. 



FIG. 58. 



I I- '.I ' I -M l 





 FIG. 59. 



Fig. 59, as indicated, really consists of two slips of paper 

 gummed together end to end. One is sensitive bromide 

 paper, ten inches in length, which has been spaced out 

 into five divisions, and marked , b, c, d, e, with an aniline 

 ink pencil. The other part is ordinary white cartridge 

 paper, slightly longer than the sensitive slip. Its purpose 

 is to serve as a handle by which to pull the sensitive paper 

 through the sleeve, and also to furnish a white surface 

 upon which a small part of the picture can be focussed, 

 that small part being confined to the central circular hole 

 in the upper card. 



Now let us see how the gauge is used in practice. It is 

 first pinned on the focussing board so that a distinctive 

 part of the image is thrown upon the central hole. In the 

 case of a portrait this should be the eye. Having focussed 

 carefully on the blank paper, the first division of the 

 sensitive slip, which will be that marked e, is pulled in 

 front of the opening. Let this be exposed for, say, fifteen 

 seconds; then pull the slip onwards, and expose d for 

 twenty seconds, c for twenty-five seconds, and so on. The 

 gauge is then taken into the dark room, its slip of sensitive 

 paper taken from its yoke-fellow, and carefully developed. 



