50 



THE BEE-KEEPERS' REVIEW. 



After the cold weather we had a thaw, ac- 

 companied by rain, showing that the outside 

 air was saturated. The air in the cellar was 

 somewhat affected by it. The dry bulb 

 showed about 48°, while the wet came up to 

 about 42^0. I then carried a half bushel of 

 uuslacked lime into the cellar. In two days 

 there was a difference of three degrees in the 

 readings of the two instruments, a greater 

 difference than had been seen at any time 

 except when artificial heat had been used. 



Mr. Larrabee writes me that the difference 

 in the readings of his thermometers in the 

 bee cellar at the college is usually between 

 1 and 1^2 degrees. When there is no fire in 

 the outer cellar for several days, the mercury 

 stands alike in both instruments, showing 

 complete saturation of the air. It is evident 

 that the cellar is a damp one. If 1 remem- 

 ber aright, it is water limed. 



1 notice in the last issue of Glean ings that 

 Mr. Hoffman prefers a damp cellar. Now 

 this is something that it may be worth while 

 to know about. A man says that his cellar 

 is of such a temiierature. We ask him, is it 

 a dry cellar ? He may say : " Oh, yes, it is 

 dry." How does he know ? In fact, does he 

 know ? And if he knows, does he know how 

 dry it is '? When we can have reports of 

 bees wintering well with such and such tem- 

 peratures, with such and such percentages of 

 saturation, then we shall begin to get some- 

 thing definite. A hygrometer is such a simple 

 thing to make and use that I wish every one 

 of my readers would make one, take daily 

 observations and send me their reports. 1 

 would be willing to tabulate them ; and then 

 let them report next spring how the bees 

 have wintered. Let us try and learn at what 

 degree of temperature and what degree of 

 saturation we may expect the best results. 



But a bee cellar is not the only place in 

 which a hygrometer may be used to advan- 

 tage. It can be used to foretell either frost 

 or rain. Now that this subject is up. perhaps 

 I cannot do better than to give two short 

 extracts from a pamphlet called "The 

 Weather," published by Robert Clarke & 

 Co., Cincinnati, Ohio. The price is only 

 twenty-five cents, and to those interested in 

 this subject, it is well worth the money. 



THE DEW POINT. 



" The air deposits a portion of its vapor on 

 all bodies that are colder than itself, and the 

 temperature at which such deposit of mois- 

 ture is made is called the Dew Point. The 

 Deiv Point may at all times be found by 

 calculation with a set of factors. 



The rule is : Multiply the factor opposite 

 the reading of the dry bulb into the difference 

 of the dry and ivet bulb thermometers, the 

 reading of the dry bulb thermometer, less 

 the product found, will be the Dew Point. 



TABLE OF FACTORS FOR COMPUTING THE DEW 

 POINT. 



EXAMPLE. 



Suppose the dry bulb reads 65° 



Wet bulb 59° 



The difference 6° 



Factor (from the table, 65° ) . . . 1.8 



Product 10.8 



Dry bulb reading 65° 



Less product 10.8 



Dew Point 54.2° 



Suppose the dry bulb reads 60.5°, and the 

 wet bulb 60°. This would show that the air 

 was very highly saturated, and, by reference 

 to the Relative Humidity Table, it would be 

 found that the percentage of humidity was 

 97. Rain could be expected, because the air 

 contained nearly as much moisture as it was 

 capable of sustaining. Computing the dew 

 point, or temperature required to condense 

 the vapor, in this case we fim^ it to be 59.5°. 

 That is to say, the temperature of the air in 

 this case has to sink less than one degree, in 

 order to produce rain. 



As a guide to the probability of rain, the 

 application of this method becomes inter- 

 esting, and is generally found reliable. 



If the mercury in both bulbs rises as the 

 day advances, rain is likely, since the tem- 

 perature of the air will naturally fall with 

 the decline of the sun. In sultry weather 

 clouds and other ' signs ' of rain may mis- 

 lead us, but if we look at the evening sky 

 and see there the fair weather red, as well as 

 consult our hygrometer, and find there a 

 considerable difference in the readings, we 

 need not apprehend rain on the morrow. 

 A rapid increase in the difference between 

 the two thermometers in the morning fore- 

 tells a fire day. An increasing difference 

 Itetween the temperature of the air and the 

 temperature of the dew point, accompanied 

 by a fall of the latter, is a certain sign of 

 fair weather. But diminishing heat and 

 rising dew point foreshow rain." 



