72 PRESERVATION OF FOOD BY REFRIGERATION ; 
In the case of refrigerating rooms, as ordinarily con- 
structed, we shall have to bear in mind, as a leading 
principle, that what is to be aimed at is the exclusion of 
heat from the exterior. A mental picture should be formed of 
a porous building, through the walls of which, in spite of all we 
can do, aconstant stream of heat is flowing. Unless the heat 
is removed as fast as it streams in, the temperature of the 
interior would rise until it became the same as that of the 
ground upon which the building rested and that of the sur- 
rounding air. The rate at which the stream of heat will 
flow into the enclosure depends, of course, entirely upon 
the material and manner of construction. 
Adopting the notation and formula as given by Box in 
his work on heat, the calculations as given in Appendix B. 
will show the method as applied to a refrigerating room for 
the purpose of ascertaining the value of U, or the quantity of 
heat flowing through the walls. It will be seen that this 
can be done in various ways, and as the /eakage depends 
entirely upon the materials used and the manner of con- 
struction, its detection and measurement is one of the most 
important items to be ascertained by the engineer in 
charge. As far as can be learned, no work has hitherto 
been published on this subject. Particular attention should 
be given to it, not only as a protection against loss of 
engine power and time, but also for the purpose of ascer- 
taining the best materials to use, and the most economical 
method to be adopted in the construction of the refrigera- 
ting chambers. 
THE PROCESS OF DECOMPOSITION. 
In order to realize fully what are the conditions necessary 
for preserving a perishable organic substance, we should 
be able to form a clear conception of what the process of 
values for the conducting power (C) of various materials used in insulating 
buildings. The value of C of charcoal being taken at °531 
Silicate Cotton ... we a "382 
Hair Felt is de “ee ae bn 5p "440 
Cotton Wool ae sep Ss ae Be ‘af "462 
She p’s Wool... sch ae 46 ae ie "515 
Infusorial Earth sof nis aie ar dh? “515 
Sawdust ... ere ane soe Bas Bic “620 
Wood and Air Space ae 500 Si oes 2) OO? 
