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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-