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MODERN FRUIT MARKETING 



unit of measure for heat is the calorie. This equals 

 the heat required to raise one kilogram of water from 

 zero to one degree Centigrade. 



Then, in measuring the transmission of heat through 

 various insulating materials, calculations are based upon 

 the number of B. T. U. that will pass through one square 

 foot of substance per hour per degree, difference in 

 temperature between the two sides of the substance. 

 This enables definite experiments to be carried on and 



Fig. 84. CORK BOARD 



the insulating value of different materials can be def- 

 initely determined. Substances which allow heat to 

 pass through readily are known as good conductors of 

 heat'. Those which retard the passage of heat are poor 

 conductors. Hence, for insulating storage houses against 

 heat and cold we always select poor conductors. 



Relative Heat-Conducting Power. From a number 

 of experiments that have been made both in the United 

 States and Europe, the following figures have been taken. 



The relative insulating value of the different ma- 

 terials are based on water as a standard. As physicists 

 use water on a basis of one for the specific gravity of 

 other liquids or solids, so in testing for insulating value 



