tion of channel iron (H); brass washer
soldered to copper (K); asbestos insulation between channel iron and
copper (J); bolt holding the whole together (I); heating wire (W) and
insulator holding it (F) shown in air-space between zinc and hair-felt;
section of one of the cooling pipes (C) and its brass support (G);
threaded rod (E) fastened into H at one end and passing through asbestos
wall with a nut on the outside; and iron pipe (D) used as spacer between
asbestos and zinc.]

In the cross-section, fig. 7, A represents the copper wall and B the
zinc wall. Surrounding this zinc wall and providing air insulation is a
series of panels constructed of asbestos lumber, very fire-resisting,
rigid, and light. The asbestos lumber used for these outer panels is 6.4
millimeters (0.25 inch) thick. To further aid in heat insulation we have
glued to the inner face of the different panels a patented material
composed of two layers of sheathing-paper inclosing a half-inch of
hair-felt. This material is commonly used in the construction of
refrigerators. This is shown as E in fig. 7, while the outer asbestos
panels are shown as F.

A detail of the construction of the walls, showing in addition the
heating and cooling devices, is given in fig. 12, in which the copper is
shown held firmly to the upright channel H by means of the bolt I,
screwing into a brass or copper disk K soldered to the copper wall. The
bolt I serves the purpose of holding the copper to the upright channel
and likewise by means of a washer under the head of the screw holds the
zinc to the channel. In order to hold the asbestos-lumber panel A with
the hair-felt lining B a threaded rod E is screwed into a tapped hole in
the outer part of the upright channel H. A small piece of brass or iron
tubing, cut to the proper length, is slipped over this rod and the
asbestos lumber held in position by a hexagonal nut with washer on the
threaded rod E. In this manner great rigidity of construction is
secured, and we have two air-spaces corresponding to the dead air-spaces
indicated in fig. 7, the first between the copper and zinc and the
second between the zinc and hair-felt.

PREVENTION OF RADIATION.

As can be seen from these drawings the whole construction of the
apparatus is more or less of the refrigerator type, _i. e._, there is
little opportunity for radiation or conduction of heat. Such a
construction could be multiplied a number of times, giving a greater
number