86 PRESERVATION OF FOOD BY REFRIGERATION ; 
heated body it is found that more heat escapes than if it 
were loosely enveloped with the same material. It has 
been previously shown that the loss of heat by conduction 
depends upon the conducting power of the substance, the 
difference in temperature between one side of the body 
and the other and the thickness of the body itself, the flow 
of heat being inversely as the thickness. This is well 
illustrated in our case by the slowness with which the thick 
hind-quarters of beef part with their heat in comparison 
with the thinner fore-quarters. While on this subject it 
should be mentioned that, when once the meat is frozen 
through to the bone, the temperature falls much more 
rapidly than it did previously, which corroborates the 
statement as to the conducting power of ice, and shows 
that it was not the outer coating of ice that prevented the 
meat from freezing inside, but the comparatively large 
amount of latent heat of liquefaction of the water con- 
tained in the meat which delayed the operation. The 
previous calculation shows the enormous amount of latent 
heat to be removed from the meat at 32°, being considerably 
more than one-half of the total, or 388 out of 686 parts. 
No indication of this work is given by the thermometer, 
which remains steadily at 32° until it is completed, and to 
those who are unacquainted with the fact, it might seem 
that something was not working properly, and measures 
taken to remedy what to them seemed a fault, and which 
would seriously interfere with the successful completion of 
the refrigeration. 
If we examine the table of Radiation (No. 2), which shows 
the increased rapidity with which a body loses heat, as the 
difference between its temperature and that of the walls of 
the enclosure increases, also the table of the Loss by 
Contact of Cold Air (No. 3), which illustrates the increased 
rapidity with which a body gives up its heat as the 
difference between its own temperature and that of the 
cold air increases, and also remember the diminished con- 
ducting power as the thickness of the body increases, we 
shall no longer doubt that instead of ‘freezing in” the heat 
and retaining it by ‘closing the pores,” the very reverse 
is the case. What has really happened when meat goes 
bad while hanging in the freezing room, is want of oppor- 
