28 CONSTRUCTIVE BEEKEEPING 



on as long as temperature of the hive walls, temperature of air 

 in the hive, and humidity of hive air, hold such relations to each 

 other that the dewpoint obtains at the inside surface of the hive. 

 All objects do not radiate heat equally well. Some part with 

 their heat or become cold faster than others. A smooth istone, 

 exposed the same as grass surrounding it, does not part with its 

 heat as readily as the grass. 



PROPOLIS 



Blackened tin has a high radiating power and is taken as a 

 standard for expressing the radiating power of other substances. 

 Give the radiating power of blackened tin as 100, rosimis 96 and 

 wood is very low. Propolis, being a rosin its radiating power is 

 almost perfect. But few substances approach this high standard. 

 It is obvious that more condensation takes place on a hive lined 

 with propolis than one where the wood is without a varnish. 

 More condensation makes more evaporation, more exaporation 

 makes more room. 



A substance like propolis that is a good radiator and absorb- 

 er, is a poor transmitter of heat. Propolis used as a varnish 

 keeps the hive heat from warming the wooden walls, and they 

 being cooler at night, give a temperature to the inside surface, 

 that condenses the water vapor fast or slow, as the difference 

 cf inside air temperature and wall temperature is great or small. 



The bees finding it necessary to separate a great deal of 

 water from the nectar, dispose of it by evaporation, but instinct 

 tells them that the air holds very little on cool nights in May and 

 June ; so to remove this moisture from the air, they varnish the 

 inside walls and make a condenser out of the hive. The process 

 is, in principle, the same as that used in distillation. 



The makers of refrigerators take advantage of condensation 

 to maintain dry air in the food chamber. A refrigerator car, 

 after years of experimenting has been finished off with several 

 coats of varnish. It has been proven, by tests, that products that 

 are inclined to sweat or absorb moisture, keep drier in a highly 

 varnished car than in one not varnished. The water vapor in the 



