98 MODERN FRUIT MARKETING 
of the different materials, water under normal conditions 
has been given the value of one. Taking then, water as 
a standard, the other materials in their relative insulat- 
ing power would be as follows: 
WEE va ale bo Ske oe in Et RE aes 1 
San wx. on aaaiwa dew een ho aaseheedes, Mare ss 1.01 
BTC ogo o sasesd nis svbuesy ab abet Sa ahs, SE Sy 2 
Gement -c-6 5.4 cee ee pee a Bee ees ema 2.25 
SGONG> hci one Send! oh oars res hemos aro A eas 2.95 
EPO 1s: 2-t,corle cs dhe ceetpaie Ae nha eumsra titan t 80 
Copper: (i csviiaei so omiay Yee ater oe ae es aides 455. 
PUGS 2eexee Mee bee atte en eieemees 0.13 
WO0d) 4... seas entaet oa had abaya Seas GaN Sera 0.14 to 0.24 
WOOL) i wilendae ted cce a Saat eee eet Bee 0.06 
Butlding paper oss swseas eevee eeeee ea 0.05 
Dead. alr spaces ccewa cannes mee ee ees 0.03 - 
It will be noted from these figures that dead air or 
confined air is the best practical insulator against heat 
or cold. The best known insulator is a vacuum. The 
principle of the common thermos bottle is simply the 
insulating from outside temperature by the use of an 
almost perfect vacuum. Also, the principles of the com- 
mon fireless cooker is a perfect insulation to keep the 
heat confined to the inside of the cooker. Wood is the 
most common of all insulating materials, and perhaps 
building paper, sheet cork, and sawdust in the order 
named are of the next in importance. As a rule, the 
harder mineral substances are poorer insulators than the 
vegetable substances, and so stone, brick or cement where 
used, have to be associated with some of the better insu- 
lating materials. 
Method of Insulation.—For the most part the outside 
of cold storage houses is built of either concrete or brick. 
These are of sufficient strength to support the weight 
