1 4 PHOTO-MICROGEAPHY 



large condenser * shown at C. The light from the limelight jet, which should be 

 a " mixed one," falls first upon a piece of ground glass which is interposed between 

 the source of light and the condenser. 



The box itself enclosing the light may be i6 inches long, 13 inches wide, and 



15 inches high. These dimensions, although large, we have found most convenient, 

 inasmuch as there is no fear of the wood becoming injured by the direct heat of the 

 limelight. A suitable chimney to allow the escape of the fumes is shown rising from 



Fig. 9 



the summit. The arrangement for turning the lime is also drawn in the diagram, but 

 as this is usually supplied with the best form of jets we need only refer to it. 



Between the light and the condenser, as before stated, we usually interpose a 

 piece of ground glass, which causes a general diffusion of light, thus rendering the 

 entire field of the photograph equally illuminated. It is not absolutely necessary that 

 the ground glass should be interposed between the condenser and the light, for there 

 are those who prefer placing it between the two lenses which compose the actual con- 

 denser itself In most condensers this is easily done, but in some the space between 

 the component lenses is so small that it will not admit anything, even the thinnest of 

 ground glass. If placed in this position, too, there is a danger which ought to be 

 pointed out, namely, that the ground glass may very possibly shake and thereby 

 scratch the surface of one or other lens, and so imperil its perfect performance. If 

 there is no room between the lenses of the condenser there is no option but to put the 

 ground glass where first mentioned, as it is not a satisfactory plan to place it between 



* We say a large condenser because a small one will not cover the slide so as to illuminate it equally unless very 

 close, which is inconvenient. 



