lacquering.

The distinctive feature of this apparatus when applied to moderate
temperatures lies in the adoption of a closed system of piping of
small bore, a certain portion of which is wound into a coil and placed
in a furnace situated in any convenient position outside the drying
chamber or hot closet. The circulation is thus hermetically sealed and
so proportioned that while a much higher temperature can be attained
than is possible with a system of pipes open to the atmosphere, yet a
certain and perfectly safe maximum cannot by any possibility be
exceeded.

The efficiency of the apparatus increases within certain limits in
proportion to the pressure employed, which fact explains the
exceedingly economical results obtained, while the fact that, owing to
the high temperature used, a small-bore pipe can be made more
effective than the larger pipes used in any open system, accounts for
the lower first cost of the Perkins' apparatus.

[Illustration: FIG. 8.--Japanning and Enamelling Oven Heated by Single
Hot-water Pipes sealed at both ends with Furnace in Rear.]

[Illustration: FIG. 9--Japanning and Enamelling Oven For Bedstead,
Ironmongery, Cash-box, and Lamp Factories.]

[Illustration: FIG. 10.--Japanning and Enamelling Stove for parts of
Sewing Machines.]

It will be seen from the various illustrations that the articles to be
treated are absolutely isolated from actual contact with the fire or