nner.

_Cooling of Rooms._--For this purpose the usual plan is to employ a
circulation of cold brine through rows of iron piping, placed either
on the ceiling or on the walls of the rooms to be cooled. In this, as
in the other cases where brine is used, it is employed merely as a
medium for taking up heat at one place and transferring it to the
ammonia in the refrigerator, the ammonia in turn completing the
operation by giving up the heat to the cooling water during
liquefaction in the condenser. The brine pipes cool the adjacent air,
which, in consequence of its greater specific gravity, descends, being
replaced by warmer air, which in turn becomes cold, and so the process
goes on. Assuming the air to be sufficiently saturated, which is
generally the case, some of the moisture in it is condensed and frozen
on the surface of the pipes; and if the air is renewed in whole or in
part from the outside, or if the contents of the chamber are wet, the
deposit of ice in the pipes will in time become so thick as to
necessitate its being thawed off. This is accomplished by turning a
current of warm brine through the pipes. Another method has been
proposed, in which the brine pipes are placed in a separate
compartment, air being circulated through this compartment to the
rooms, and back again to the cooling pipes in a closed cycle by means
of a fan. This plan was tried on a large scale by Mr. Chambers at the
Victoria Docks, but for some reason or other was abandoned. One
difficulty is the collection of ice from the moisture deposited from
the air, which clogs up the spaces between the pipes, besides
diminishing their cooling power. This, in some cases, can be partially
obviated by using the same air over again, but in most instances
special means would have to be provided for frequent thawing off, the
pipes having, on account of economy of space and convenience, to be
placed so close together, and to be so confined in surface, that they
are much more liable to have their action interfered with than when
placed on the roof or walls of the room.

In addition to the foregoing there are, of course, many other
applications of ammonia refrigerating machines of a more or less
special nature, of which time will not permit even a passing
reference. Many of these are embraced in the second class, cold water
or brine being used for the cooling of candles, the separation of
paraffin, the crystallization of salts, and for many other purposes