Cork insulation; a complete illustrated textbook on cork insulation ...

326 CORK INSULATION
on the "Mechanical Production of Cold," being simply a re-
versed Sterling air engine, the air working in a closed cycle
instead of being actually discharged into the room to be cooled,
as is the usual practice with compression machines. It is
said that Kirk's machine was used commercially with success
on a fairly large scale, chiefly for ice making, producing about
4 pounds of ice per pound of coal.
In 1870, the subject of refrigeration was investigated by
Professor Carl Linde, of Munich, Germany, who was the first
to consider the question from a thermodynamic point of view.
He dealt with the coefficient of performance as a common basis
of comparison for all machines, and showed that the compres-
sion vapor machine more closely reached the theoretical maximum
than any other. Linde also examined the physical prop-
erties of various liquids, and, after making trials with methylic
ether in 1872, built his first ammonia compression machine in
1873. In the next two years, these machines were introduced
into the United States by Professor Linde, and David Boyle
of the United States. From then until the ice shortage of
the summer of 1890, many new forms of apparatus were produced
and certain important improvements were made, follow-
ing which the rapid development and practical utilization of
the art of ice making and refrigeration grew by leaps and
bounds, until today ice and refrigeration may be had at any
time and anywhere that power can be obtained.
149.—Early Methods of Utilizing Ice as a Refrigerant.—
Just as snow was used in ancient times to cool the cup that
cheered, so harvested natural ice was probably first employed
in later times to cool wines and preserve beer. Deep cellars
were dug, walled with heavy masonry, and divided longitud-
inally by arched stone ceilings into top cellars and sub-
cellars. The goods to be preserved were placed in the lower
or sub-cellars and the ice was filled into the top cellars just
above, an ingenious and effective arrangement that permitted
the storing of sufficient quantities of natural ice, as harvested,
to carry the sub-cellars through the warm summer months at
temperatures cool enough for many purposes. Such cellars
were probably the first man-made cold storage houses or