Unit of Candle-power in White Light. 



83 



are equally likely to occur conjointly ; or (b) if a definite 

 relation exists between any of the variables not satisfying 

 condition (a). 



An examination of the observed values of humidity, tem- 

 perature, and barometer reveals that condition (a) is fulfilled 

 by the values of humidity and barometer or by the values of 

 temperature and barometer, but that the humidity and tem- 

 perature values satisfy neither condition (a) nor condition 

 (6). This last fact is illustrated in fig. 4, where the simul- 

 taneously observed values of humidity and temperature 



























Fig 



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Observa 



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Tcmpercturc (C°). 



Diagram showing Values of the Temperature and Humidity of the Air 

 over the Period during which observations were made on the 

 Candle-power of the Pentane Lamp. 



obtained whilst observing the candle-power of the pentane 

 lamp both in 1904-06 and 1912-14 are plotted. It is seen 

 that a loose general relation exists between these variables, 

 the lines A and B representing the best linear relation for 

 the two sets of experimental data, and so to some extent 

 condition (b) is fulfilled. 



If, now, it is assumed that the linear relationship shown 

 by lines A and B in fig. 4 actually exists between these 

 values of humidity and temperature, the following are the 

 values which result for the coefficients A, B, and in the 

 above equation (3) : 



C.P.=10 f 0-187(8-«)-0-008 5 (760-6)-0'076 fi (12-0 (4) 



G2 



