ARTIFICIAL REFRIGERATION AND ICE MAKING. XXXIX. 
has been due more to its use in the brewery and the national taste 
for iced water than to other applications, and that in New South 
Wales the idea of freezing food products for export—first suggested 
in 1860 by the late Mr. Augustus Morris, when he offered to 
contribute £1000 towards the experiment of sending frozen meat 
to England—was the main factor which induced the late Mr. T. 8 
Mort to devote his energies and probably a quarter of a million 
sterling towards the economic production of artificial cold. For 
more particulars as to Mr. Mort’s great work the author would 
refer those interested, to an article in “ Ice and Refrigeration.”! 
HOW CAN A MACHINE PRODUCE COLD. 
Seeing that all machines work with more or less friction, and 
that the power thus lost reappears in another form of energy as _ 
heat—which is sensible and apparent—there is some excuse for 
the difficulty felt by the ordinary lay mind in comprehending the 
production of cold by machinery. It may be said at once that 
no combination of mechanism—with unlimited power to drive it— 
Could alone make ice from water, and that an ice machine is 
‘Simply an instrument for dealing with a medium in such a way, 
that it, the medium, is enabled to take up heat from the body to 
be cooled, and transfer it to another body. Except under very 
Special circumstances which will be referred to later on, this heat 
is transferred to the water which is used for the purpose of con- 
densation and goes to waste. 
TWO CLASSES OF MEDIUM USED. 
There are two distinct systems of mechanical refrigeration in 
Use, operating by means of a medium. Under the more simple 
system this medium is a permanent gas which is alternately com- 
Pressed and expanded, and is not liquefied under compression. 
In actual practice atmospheric air is alone used for this purpose 
and the machines are termed compressed air machines. Under 
& more complex system of mechanical refrigeration a volatile 
medium is employed, and in the operation of the machinery there 
1 An (American Journal) August 1895. 
