FIFTEENTH ANNUAL YEAR BOOK — PART VIII. 517 



of holding more water vapor and relative humidity is simply an expres- 

 sion of the percentage present compared with all that the atmosphere 

 can hold. However to maintain a temperature of 96° F. necessitates the 

 consumption of much more honey and this in turn gives off much more 

 water vapor. Consequently with a cellar temperature of 45° P. we should 

 expect much more condensation in a colony with a cluster temperature 

 of 96° F. than in one with a cluster temperature of only 65° F., except 

 that the increased heat would tend to produce stronger currents of air 

 in the hive which might relieve the situation somewhat. Since 96° F. is 

 about brood rearing temperature it is partly indicated why brood rearing 

 during the winter confinement may be highly injurious, as it is usually 

 held to be. It may be stated that a cellar temperature of 45° F. and a 

 cluster temperature of 60'° P. might not occur; the other temperatures 

 used in the table might well occur under different conditions. 



In making determinations of relative humidity it is necessary to take 

 into account the barometric pressure but in any given locality the changes 

 of the barometer are so small as to be negligible and therefore need not 

 be discussed here. In any event in using wet and dry bulb thermometers 

 the conversion table used must be for the right barometric pressure. 



A further word of warning concerning the use of wet and dry bulb 

 thermometers may not be amiss. To obtain accurate results the air must 

 be moving past the bulbs at the minimum rate of 15 feet per second and 

 if this is not occurring naturally the thermometers must be whirled at a 

 corresponding rate. Unless this is done the readings are entirely worth- 

 less. Great care must be taken not to read the wet bulb thermometer 

 until it registers as low as it will fall. It is therefore obvious that wet 

 and dry bulb thermometers hung in the bee cellar and not whirled give 

 no reliable data as to the relative humidity of the cellar. Many beekeepers 

 thus use them incorrectly. 



HOW MOISTUBE ESCAPES FROM THE HIVE IN WINTER. 



During the summer when nectar is being ripened into honey, great 

 quantities of water leave the hive in the form of water vapor. During 

 this period the hive is being well ventilated by fanning bees so that the 

 atmosphere is changed rapidly and, being warm, is capable of taking up 

 more moisture than is the atmosphere of the bee cellar. In winter when 

 the bees are in a cluster this ventilation by fanning does not occur. The 

 amount of water that must leave the hive is much less than in summer, 

 but on the other hand it either must pass out in air set in motion by 

 changes in temperature, or will condense on the frames, combs and hive 

 and possibly run out of gravity. 



If the atmosphere of the bee cellar is heavily charged with water vapor, 

 as is frequently the case, that within the hive must be saturated. The 

 additional water produced by the bees will therefore condense and run 

 out the entrance. It frequently happens that the air inside is saturated 

 while that outside is capable of taking up this moisture again by evapora- 

 tion, so that there may be no water visible except within the hive, most 

 often on the cover, and possibly also on the bottom board. 



