THE BOOK OF THE LANTERN. 9 



Originally for such effects two separate lanterns were 

 used side by side, but now a biunial lantern, with one 

 optical system above the other, is employed (see fig. 5). 

 The modern arrangement is far more convenient for the 

 operator, for the apparatus is compact and every adjustment 

 is within easy reach of his hand. A lantern so constructed 

 generally consists of a strong wooden body, lined with metal, 

 with cells for the reception of the condensing lenses. 

 Openings at the back shaped thus JL allow for the necessary 

 to and fro motion of the lime jets and their trays. 

 Between these openings, on the outside of the lantern 

 body, is fixed the dissolving key or tap, connected by india- 

 rubber tubes with the two jets (see fig. 6). In front of the 



FIG. 6. 



instrument are the stages for the reception of the slides, and 

 the metal plates to which are affixed the telescopic tubes for 

 holding the objective lenses. These plates are hinged, and 

 their inclination upward or downward to make the two 

 discs concentric on the sheet or screen is governed by 

 milled headed screws. The objectives can by this means 

 be made to slightly approach one another, while the con- 

 densers remain fixed. It is obvious that it would be better 



