bonic acid cylinder, CO squared, the cock, Ro, of the
latter is turned full on. The cock of the worm, which is closed, is
opened slightly. The vaporization and expansion of the liquid carbonic
acid cause it to congeal in the form of snow, which distributes itself
and circulates in the worm, S, and then in R. The flakes thus coming in
contact with the metallic sides of S rapidly return to the gaseous state
and produce an energetic refrigeration. At the lower part of the annular
space, R', are placed fragments of sponge impregnated with alcohol. The
snow that has traversed the worm without vaporizing reaches R'. and
dissolves in this alcohol, and the refrigeration that results therefrom
completes the lowering of the temperature. The gas finally escapes at O,
and then through the bent tube, T".

[Illustration: CAILLETET'S CRYOGEN.]

The apparatus may be constructed with an inverse circulation, the
carbonic acid then entering the annular vessel, R, directly, and
afterward the worm, S, whence it escapes to the exterior of the
apparatus. The expansion cock sometimes becomes obstructed by the
solidification of the snow. It will then suffice to wait until the
circulation becomes re-established of itself. It may be brought about by
giving the cock, Ro', a few turns with the wooden handled key that
serves to maneuver the latter. It is not necessary to have a large
discharge of carbonic acid, and consequently the expansion cock needs to
be opened but a little bit. A few minutes suffice to reduce the
temperature of the alcohol bath to 70 deg., with an output of about from 41/2
to 51/2 lb. of liquid carbonic acid. When the circulation is arrested, the
apparatus thus surrounded by its isolating protective jackets becomes
heated again with extreme slowness. In one experiment, it was observed
that at the end of nine hours the temperature of the alcohol had risen
but from 70 deg. to 22 deg.. On injecting a very small quantity of liquid
carbonic acid from time to time, a sensibly constant and extremely low
temperature may be maintained indefinitely.--_Le Genie Civil_.

* * * * *

METHOD OF PRODUCING ALCOHOL.

In carrying out my improved process in and with the apparatus employed
in ordinary commercial distilleries, says Mr. Alfred Springer, of
Cincinnati, O., I preferably employ separate vats or tubs for the nitric
acid solution and the material to be treated, and a convenient
arrangement is to