244 THE BOOK OF THE LANTERN. 



The instrument can be made either complete in itself, as 

 shown in the cut, or it can be fitted to any good optical 

 lantern. In the first case, it is provided with a triple 5-in. 

 condenser, which insures the maximum amount of light, 

 and in the latter case the lantern condenser, of whatever 

 form it may happen to be, is brought into use. The 

 illustration gives a very fair idea of this instrument, by 

 which the relation of its various parts can be well under- 

 stood. It has a coarse adjustment focussing screw, as 

 well as one for fine adjustment. The tube in front of the 

 objective is for the reception of various lenses to give 

 extra amplification, and the necessary alum-tank is let 

 into the brass front tube, midway between its supporting 

 pillar and the large condensers. The details of the stage 

 and revolving diaphragm plate are much the same as in 

 the instrument last described, but the substage condensers 

 are 'of varying foci, and are suited to the different objec- 

 tives employed. The milled head immediately above the 

 pillar is in connection with a rack tube, which provides the 

 necessary distance adjustment for these condensers. 



THE OPAQUE LANTERN. 



It will be at once conceded that most objects, animate 

 and inanimate, can be photographed, and that such photo- 

 graphs can be used as lantern pictures. But there are 

 still others which cannot be so treated, or rather, which 

 can be better shown as opaque objects. The worker with 

 the microscope will be able to appreciate the possibility 

 of showing, by means of the lantern, objects which are 

 not transparent. Some of the most beautiful effects 



