190 



THE BOOK OF THE LANTERN. 



range matters in a very simple manner. Let the lantern 

 stand on a base board, and let the objective be supported 

 upon a sliding piece in front of that board. Cut away the 

 tin nozzle upon which the objective fits in the ordinary 

 way, so that any object can easily be brought between 

 condenser and objective. Or to still more simplify the 

 matter, we can use the lamp only of one of these mineral 

 lanterns and place it as figured in the annexed cut (fig. 50). 



FIG. 50. 



FIG. 51. 



Here we have a base board A A, with a fixed support in the 

 centre B, which is pierced with a hole sufficiently large to 

 contain the condensers of the lantern. Close up to this 

 is placed the lamp L. Another support, C, holds the objec- 

 tive, and this support by means of a sliding piece let into 

 the base board, can be moved to and fro for focussing pur- 

 poses in front of the condensers. It will be seen that by 

 adopting this arrangement, no lantern is necessary. We 

 simply require the illuminator, which must of course be 

 closed in, as sold with most lanterns ; a condensing lens ; 

 and an objective. 



The number of beautiful experiments which are possible 

 with the use of a glass tank, or rather, several glass tanks 

 of the simple form shown in fig. 51 are surprising. Most 



