EGGS IN COLD STORAGE. 23 



and distribution of the air circulation employed. (See 

 Chapter III on "Circulation.") 



CORRECT RELATIVE HUMIDITY FOR A GIVEN TEMPERATURE 

 IN EGG ROOMS. 



Temperature Relative Humidity, Humidity table 



in Decrees F. Per Cent. for egg rooms. 



29 78 



30 76 



31 74 



32 71 



33 69 



34 67 



35 65 



36 62 



37 60 



38 58 



39 56 



40 53 



There are two kinds of instruments in use for de- Hygrometers. 

 termining- humidity, hygrometersand psychrometers. 

 The hygrometer depends on the expansion and con- 

 traction of some substance, as a human hair, in the 

 presence of more or less moisture in the air. The 

 hair used is fastened at one end, the other end passing- 

 around a pulley, to which is fastened a pointer, which 

 moves over a graduated arc as the hair chang-es its 

 leng-th. The scale reads from to 100. The chief 

 advantag-e of these instruments is that results are 

 obtained at once, the reading- corresponding- to the 

 percentag-e of saturation or relative humidity; but 

 these instruments are affected by chang-es of tem- 

 perature, and shocks or vibration materially affect 

 the reading-. Further, they are more expensive in 

 first cost, and not so convenient to use, as they must 

 hang- for some time in the room to be tested, while 

 with the sling psychrometer, described in another 

 paragraph, an observer can pass from room to room, 

 g-etting- observation in less than two minutes in each 

 room, needing- but one instrument and making- all 

 observations at practically the same time. 



A psychrometer is simply two thermometers Psychrometers. 

 mounted on a frame ; the bulb of one being- covered 



