Lantern bodies as a rule are now made of metal, although up till quite recently the better class instruments were more usually made of polished mahogany lined internally with iron; but there has of late been a consensus of opinion in favour of metal only.
In the cheaper lanterns this metal body is usually made either of Russian iron or of sheet-iron tinned and japanned,
there being little to choose either in price or quality between the two varieties, and in all but the very cheapest instruments the front is usually of brass.
In better lanterns the body is more often made of enamelled steel, the front as before being of brass; but brass, copper, or aluminium are also used occasionally for the body of the lantern.
In deciding upon the type of body to be purchased the main considerations to be borne in mind are: (1) The type or types of illuminant to be used, a powerful arc lamp for example requiring a larger body than is necessary for a weaker radiant; (2) the size and position of the lens to be carried, a Petzval objective of say 3 inches diameter which has to be supported at the end of a long brass mount for long-range work obviously demanding a body of greater strength and rigidity than is required with a 6-inch focus lens of 2 inches diameter; (3) price.
Fig. 42 shows an extremely good lantern body for short-range work made by Messrs. Hughes, the illustration depicting the instrument complete with a 'Luna' methylated spirit lamp, though, of course, any other illuminant suitable for a small lantern could be used instead.
This lantern illustrates well one point that has already been emphasised as important, viz. the ventilation of the condenser. It will be noticed that this is placed outside the body of the instrument instead of inside as is usual with larger bodies, and that wide slots are cut in the condenser mount to allow free escape of steam.
Other points of this excellent design are the screw adjustment to the slide stage (facilitating the use of special slides, such, for example, as those illustrating the movements of the planetary bodies which sometimes involve the use of extra thick frames) and a simple but efficient tilting arrangement to the base.