yes.
The great sides of beef, hung in rows, were frozen as hard as rock. Even
after the strip of water had been crossed on the return journey and the
meat exposed to the full, unobstructed glare of the sun the cruiser's
messcooks had to saw off their portions, and the remainder continued
hard as long as it lasted. But the satisfaction of the men who ate that
fresh American beef cannot be told.

Cream from a famous dairy is sent to particular patrons in Paris,
France, and it is known that in one instance, at least, a bottle of
cream, having failed to reach the person to whom it was consigned, made
the return transatlantic voyage and was received in New York three weeks
after its first departure, perfectly sweet and good. Throughout the
entire journey it was kept at freezing temperature by artificial
means. These are but two striking examples of wonders that are performed
every day.

[Illustration: THE TYPE MOULDS
Moulds for 225 different characters are contained in this frame.]

Cold, of course, is but the absence of heat, and so refrigerating
machinery is designed to extract the heat from whatever substance it is
desired to cool. The refrigerating agent used to extract the heat from
the cold chamber must in turn have the heat extracted from it, and so
the process must be continuous.

Water, when it boils and turns into steam or vapour, is heated by or
extracts heat from the fire, but water vapourises at a high temperature
and so cannot be used to produce cold. Other fluids are much more
volatile and evaporate much more easily. Alcohol when spilt on the hand
dries almost instantly and leaves a feeling of cold--the warmth of the
hand boils the alcohol and turns it into vapour, and in doing so
extracts the heat from the skin, making it cold; now, if the evaporated
alcohol could be caught and compressed into its liquid form again you
would have a refrigerating machine.

Alcohol is expensive and inflammable, and many other volatile substances
have been discarded for the one or the other reason. Of all the fluids
that have been tried, ammonia has been found to work most
satisfactorily; it evaporates at a low temperature, is non-inflammable,
and is comparatively cheap.

The hold of the supply-ship mentioned at the head of this chapter was a
vast refrigerator, but no ice was used except that produced mechanically
by the power in the ship. To produce the cold in the hold of the ship it
was necessary to extract the heat i