134 THE BOOK OF THE LANTERN. 



Melt by heat, but not above 120 Fahr. Then in a 

 yellow light, pour B into A, stirring rapidly all the time, 

 and finally adding C. Allow the emulsion thus made to 

 remain for one hour, at the temperature already stated, 

 and then put aside in a dish to set. The washing, filtering, 

 and coating operations are the same as those described for 

 bromide plate making. The bright yellow light allowable 

 is a great help to comfortable working of this process. 



Chloride plates are useless, on account of their slowness, 

 where a slide has to be reduced, by means of the camera, 

 from a negative larger than itself. Nor do I advise the 

 amateur to adopt them unless he can work by daylight, 

 or is fortunately situated like one I know, who lives oppo- 

 site to an enterprising tailor who displays an electric arc 

 light in front of his door. For the chloride plate is most 

 insensitive to yellow light, such as that afforded by gas. 

 For this reason, most commercial makers advise that the 

 light chosen should be that procured by burning an inch of 

 magnesium wire at a distance of so many inches from the 

 printing-frame. This advice is not difficult to follow, but 

 it is very difficult to make two pieces of wire give out 

 exactly the same amount of light ; for magnesium wire has 

 a habit of dropping down in a languid manner under the 

 influence of its own heat, and going out suddenly when it 

 ought to shed its radiance abroad. With diffused daylight 

 all is plain sailing. The negative, with its chloride plate 

 in contact with it, is exposed, say, for three seconds to 

 daylight, and is then dropped into the developer. Here 

 is a good one, devised, if I remember rightly, by 

 Mr. Edwards : 



