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BELL SYSTEM TECHNICAL JOURNAL 



room." in wliich the apparatus was located, was iindor a thcriiiostatic 

 control which allow-ed a temperature \ariation of approximately 

 ±0.5° F. However, the calibration of the resistance thermometers 

 and the sensitivity of the bridges in which they arc placed is such 

 that temperatures and temperature differences are recorded wiih an 

 accuracy of ±]^° F. 



]-'ii;i.i) Trials 



In order to determine just what combinations of temperature and 

 relative humidity pre\ail in wideK- separated localities of the United 

 States, certain cities were selected in wiiich nioislure troubles with 



Fig. 6 — Comparison of Indoor and Outdoor Temperatures and Relative 

 Humidities at Savannah, Cla. 



telephone (•(|iiipniciit miRht be exjiected to occur, and at whidi local 

 stations of the I'liiled States Weather Bureau were ioc.iicd. so that 

 comparisons might be made between our records of indoor ((indiiions 

 and the f)bservations of outdoor conditions. 



Ten of these instruments were installed in ccniral < tliccs in New 

 York (3), Boston, Savannah, New Orleans. Chicago, Minneapolis, 

 Houston and Seattle, from which records lia\e bei'ii obtained during 

 the summer months of 1921 anfl 1022. 



