$02 



Experimental Researches on the Depressions 



[July, 



and a greater dryness consequently attained ; though in some cases I 

 had not the patience to wait until the hygrometer marked : in fact, 

 if it did, there was usually enough of moisture in the passages of the 

 gasometer to cause a fall of 1 or 1^ degrees in the tell-tale hair hygro- 

 meter, ere the air reached the vent. 



Tab. II. 2nd pt. — Maximum Depressions determined at Calcutta. 



Temp, of 



Wet-bulb Observed 



Barom. 



Hair 



Corrected 



Corrected 



Aqueous 



Quotient 



dry air 



Therm. 



depression 



at 32° Hygrom. 



depression. 



wet-bulb 



tens, at t' 



of 



t 



t' 



d 



B 



H 



D 



t> 



/' 



D -f/' 



o 



o 



o 







o 



o 



in 





94.8 



57.8 



37.0 



29.67 



5 



38.7 



56.1 



.459 



84 



94.fi 



57.3 



37.3 



.51 



1? 



■A7.7 



56.9 



.471 



80 



96.4 



58.4 



38.0 



.43 



2 



40.0 



56.4 



.462 



82 



92.0 



56.1 



35.9 



.50 



3 



37.0 



55.0 



.442 



84 



88.7 



54.4 



34.3 



.55 



3 



35.2 



52.5 



.406 



86 



87.0 



54.8 



32.2 



.44 



4? 



33.4 



53.6 



-420 



79 



83.1 



52.1 



32.0 



.50 



2 



32.5 



50.6 



.381 



85 



88.2 



54.5 



33.7 



.46 



3 



34.6 



53.6 



.420 



82 



82.6 



51.7 



30.9 



.50 



2 



31.4 



50.2 



.376 



84 



80.9 



51.1 



29.8 



.55 



1 



30.1 



50.8 



.384 



78 



The same uniformity in the quotients of the last column will be 

 remarked in these two tables, but the average is now 81.8, considerably 

 higher than the Paris result. 



Having thus by the ordinary atmospheric temperature of a Cal- 

 cutta laboratory in May, brought up my train of observations to 

 96° ; and finding that the depressions so much exceeded those for the 

 same portion of the series ascertained at Benares by suspending a 

 wet-bulb thermometer in a vessel of sulphuric acid heated succes- 

 sively from 90° to 140°*, I devised the following method of extending 

 the dry-air current series to temperatures still more elevated. 



In the first place, the gas-pipe of the gasometer was encased for 

 about four feet of its length in a larger leaden pipe connected with 

 my small steam engine, so that a current of steam could be main- 

 tained in the latter during the continuance of the experiments, as 

 is shewn in fig. 2. PL XXI. The extremity of the gas-pipe terminated 

 in a glass tube holding, first, a dry thermometer, and an inch further 

 on, the wet-bulb thermometer, inserted through corks. 



On letting on the steam, (the two thermometers being stationary at 

 92°,) one began to rise rapidly, while the other fell very slowly. I 

 could not, however, succeed in getting the former to rise beyond 1 90°, 

 though the steam itself was at 215°. The wet-bulb then stood at 85°.0 

 and it fell to 80°.4 at 180° :— 80 at 170, and 79.5 at 166. The 



* See Gleanings, I. 79. I purposely exclude these results in the present 

 place, lest they should confuse the view ; but they are, nevertheless, valuable ia 

 another sense, as shewing the difference, between the depression in calm air and 

 in a current. 



