HYGROMETRIC RESEARCHES. 



549 



As a new series of experiments was begun with 184, the difference in sign of the 

 larger number of deviations in the two series must be explained by some slight difference 

 in the working. On the dry day of 4th September 1893, Nos. 153-164, the deviations 

 varied from +0*70 to —0*14, and if the first experiment of the day, which has an 

 abnormally large deviation, be eliminated, the deviations vary from +0'39 to —0*14. 



The greatest variations occurred in the afternoon, when the calculated value for the 

 water vapour exceeded that determined. On 10th September 1894, Nos. 185-192, 

 another very dry day, the deviation varied from to +0*25. 



From the present determinations it is not possible to have any certain relationship 

 between these deviations and the time of day. Some of the more excessive deviations 

 are the first for that day, but this is not always the case ; some may be due to the 

 lessening of the drying power of a tube in its last experiment. The deviations have 

 also been tabulated according to the departures of the wet bulb from the dry, and 

 eliminating experiments 137, 153 and 169, and the doubtful results of 207, 210, 211, 

 this gives the following table : — 



Number and Mean Value of Deviations of Observed from Calculated Values of Means of Water 

 Vapour arranged according to Differences between Dry and Wet Bulb Thermometers. 



t—t' 



Experiments 133-183. 



Experiments 184-223. 



+ 



- 



+ 



No. 



1 

 3 



1 

 2 

 3 



Mean value. 



No. Mean value. 



No. 



Mean value. 



No. 



Mean value. 



Under 0-5 . 

 0-5 to 1-0 . 

 1-0 to 2-0 . 

 2-0 to 5-0 . 

 Over 5-0 . 



0-25 

 0-22 

 0-30 

 0-28 

 0-27 



8 

 6 

 8 

 4 



7 



0-17 

 0-28 

 017 



o-io 



0-07 



10 



5 



4 



3 

 13* 



0-26 

 0-16 

 0-09 

 0-19 

 0-18 



1 



o 



1 



0-09 

 0-21 



0-31 



The greatest variations are in the cases where dry and wet bulb readings are closest, 

 as the following table shows : — 



t'—t' 



133-183. 



184-223. 



i 

 133-223. 



+ 



- 



+ 



+ 



— 



Under 1 

 Over 1 



4 

 6 



0-23 

 0-28 



14 



19 



0-22 

 0-12 



15 

 20 



0-23 ' 1 

 0-16 | 3 



0-09 

 0-24 



19 

 26 



0-23 

 0-19 



15 

 22 



021 

 0-13 



In addition two experiments gave the same results of calculation and by direct determination. 



