THE BOOK OP THE LANTERN. * 223 



for slides transparent positives on glass, and it stands to 

 reason that, if the sheet or surface upon which the image 

 is thrown were, by chemical means, to be made sensitive 

 to light, we should obtain much the same result that we 

 get by means of our camera, a negative image, which can 

 be rendered visible by development. If, on the other hand, 

 we employ one of our little negatives as a lantern slide, 

 we can produce from it a positive. Such is the theory 

 which we will now endeavour to reduce to practice. 



The lantern employed can be of the ordinary kind used 

 for projection, but in this case, where the condenser only 

 measures 4 inches, it is obvious that a negative measuring 

 less than that size will be the only one available. The 

 operator will therefore be better off with a lantern made 

 specially for enlarging purposes, the condenser of which 

 must be at least 5 inches in diameter to accommodate a 

 quarter-plate negative. It might, in many cases, be prac- 

 ticable to fit the ordinary lantern with a condenser of that 

 size when it is proposed to use it for enlarging purposes. 

 Whatever be the arrangement, there must be in front of 

 the lens of the lantern a flat board upon which the image 

 can be projected, and which .will serve as a support for the 

 sensitive surface at a later stage of the operations. 



A convenient form of upright easel is shown at fig. 56. It 

 can be moved backwards and forwards between a couple of 

 laths nailed on the floor, while the enlarging lantern 

 remains stationary. A light-tight box above it contains a 

 roll of sensitive paper, which can be pulled down and cut 

 off in lengths as required. This easel has a hinged frame, 

 so that when a sufficient length of the paper is drawn down 



