1836.] 



of the Wet-bulb Hygrometer. 



40 r 



the depressions divided by these tensions, which will be found to be 

 the key to the formation of a formula for the problem. 



Tab. I. — Depressions observed by M. Gay Lussac. 

 Temp, of Wet-bulb Depression Aq. tens. Qut. of Temp, of Wet bulb Depression Aq.tens. Qut. of 



dry air 



t 







32.0 

 33.8 

 35.6 

 37.4 

 39.2 

 41.0 

 42.8 

 44.6 

 46.4 

 48.2 

 50.0 

 51.8 

 53.6 



therm. 

 V 

 o 



22.0 

 22.8 

 24.1 

 25.4 

 26.9 

 27.9 

 29.1 

 30.2 

 31.5 

 32.7 

 33-9 

 34.9 

 36.1 



wet-bulb 



D 



o 



10.0 

 11.0 

 11.5 

 12.0 

 13.3 

 13.1 

 13.7 

 14.4 

 14.9 

 15.5 

 16.1 

 16.9 

 17.5 



at f 



f 

 in 

 .139 

 .143 

 -153 

 .157 

 .166 

 .172 

 .179 

 .186 

 .195 

 .204 

 .213 

 .220 

 .231 



D-i-/ 



72 



76 

 75 

 76 



74 

 76 

 76 

 72 

 77 

 76 

 75 

 77 

 76 



dry air. 

 t 

 o 



57.2 

 59.0 

 60.8 

 62.6 

 64.4 

 66.2 

 68.0 

 69.8 

 71.6 

 73.4 

 75.2 

 77.0 



therm, 

 o 

 38.7 

 39.5 

 40.6 

 41.7 

 42.9 

 44.0 

 45.1 

 45.2 

 47.3 

 48.4 

 49,5 

 50.5 



wet bulb. 



D 







18.5 

 19.5 

 20.2 

 20.9 

 21.5 

 22.2 

 22.9 

 23.6 

 24.3 

 25.0 

 25.7 

 26.5 



at f. 



/' 



in 



.252 

 .260 

 .268 

 .280 

 .292 

 .304 

 .316 

 .317 

 .340 

 .354 

 .363 

 .380 



D-r-/ 



73 

 75 

 75 

 75 

 73 

 74 

 72 

 74 

 71 

 70 

 71 

 70 



Average ratio of depression to aq. t., 74 

 It will be remarked, that with exception of the three or four last ex- 

 periments, the depression follows a nearly uniform ratio to the aqueous 

 tension, being 74 times greater. The air in the last four was doubt- 

 less not quite so dry as in the others ; for in my own first series, which 

 begins nearly where the French table leaves off, the depressions are 

 found considerably in excess of M. Gay Lussac's results. 



In the series in question the presence of the hair hygrometer enables 

 me to make an approximate correction for imperfect dryness founded 

 on a coincidence, which will be explained hereafter, between the curve 

 of depressions and the curve of the hygrometer, so that nine degrees 

 of the latter + or — , for instance, will nearly represent 9 per cent, -f 

 or — in the depression, near the dry extremity of the scale*. The baro- 

 metric correction will be also explained further on. 



Tab. II. — Maximum Depressions determined at Benares. 



Temp, of 



dry air 



t 



Wet-bulb Observed 

 Therm, depression. 

 t' d 



Barom. 

 at 32° 

 B 



Hair 



Hygrom. 



H 



Corrected 

 depression. 



D 



Corrected 

 wet bulb 

 t' 



Aqueous 

 tens, at t' 



f. 



Quotient 

 of 



72.5 



47.2 



25.3 



29.43 



9.5 



27°.5 



45t0 



in 

 .315 



87 



75.0 



48.2 



26.8 



.52 



9.5 



29.3 



45.7 



.321 



91 



78.5 



52.1 



26.4 



.30 



9.5 



29.3 



49.7 



.369 



78 



82.6 



54.8 



27.8 



.26 



9.5 



30.3 



52.3 



.403 



75 



83.5 



54.5 



29.0 



.25 



8. 



31.3 



52.2 



.402 



77 



84.7 



55.0 



29.7 



.30 



9.5 



32.3 



52.4 



.405 



80 



85.0 



55.0 



30.0 



.30 



8 



32.2 



52.8 



.411 



80 



85.0 



54.8 



30.2 



.20 



8 



32.5 



52.5 



.407 



80 



90.2 



56.8 



33.4 



.15 



9 



36.1 



54.1 



.429 



82 



90.3 



56.7 



33.6 



.15 



8 



35.9 



54.4 



.434 



83 



In continuation of the foregoing, I will now give the Calcutta 

 series, in which sulphuric acid was used in lieu of chloride of lime, 



* This mode of correction was not adopted in my former paper, and the de- 

 pressions were consequently too low. 



3 F 



