10 THE BOOK OF THE LANTERN. 



if the condensing lens also moved with the objective so 

 that the optical axis of one should agree with the 

 other. This could easily be done by making the upper 

 lantern move on a central pivot, and clamping it with a 

 fixed screw ; but the more faulty and elaborate plan has 

 been adopted by manufacturers, and will probably hold its 

 own for a long time yet. 



It is certainly too much the fashion to adorn lanterns 

 with a mass of heavy brass-work. Like any other adorn- 

 ment, the brightly-lacquered brass looks well enough, but 

 represents, to my thinking, a waste both of material and 

 of workmanship, which adds greatly to the cost of an 

 instrument, without adding one jot to its efficiency. In- 

 deed, this brass-work is a positive disadvantage when a 

 lantern has to be carried from place to place by a busy 

 lecturer, and constitutes, not only an inconvenience, but a 

 tax, in the shape of "excess luggage." This superfluous 

 metal must, I suppose, be looked upon as a custom of the 

 trade, which it is very difficult to break down. It is the 

 same case with the microscope, the delicate brass-work of 

 which often costs more than the lenses, expensive though 

 the latter are. In each case the metal-work represents a 

 convenience in operating the instrument, but much of it 

 could be dispensed with, without in any way detracting 

 from its performance. We may, I think, gain a lesson 

 in the construction of an ideal lantern by examining 

 a modern photographic camera for tourists' use, where the 

 greatest rigidity is combined with extreme lightness, and 

 metal is used but sparingly. Looking at such an 

 instrument, we find that it must be extended for focus- 



