414 



Experimental Researches on the Depressions 



[J ULT, 



tion. This I only discovered on checking all the instruments, as is 

 my custom, before commencing the present experiments ; but the 

 hygrometer has been untouched during the interval, and as its scale 

 embraces the 100 degrees with as much sensibility as when it was 

 constructed in 1825, there can be no hesitation in making the required 

 correction throughout. The extreme points of this instrument should 

 indeed be verified at least once in a year ; as the index point is, from 

 its delicate construction, easily shifted 2 or 3 degrees. 



Tab. V. — Comparison of the monthly averages of the Wet-bulb depression, 

 and the Hair-hygrometer , for 3 years in Calcutta. 







At 



10 A. M. 





Tension, 





At 4 p. m. 





Tension, 







Temp. 



Dep. 



Hyg. 



by Dep. 



by Hyg. 



Temp. 



Dep. 



Hyg. 



by Dep. 



by Hyg 



Jan. 1833 



68.0 



8.4 



81 



.55 



.61 



72-4 



11.6 



74 



.47 



.49 



1834 



67.5 



6.4 



83 



.64 



.64 



71.1 



9.2 



76 



.53 



.52 



1835 



67.8 



8.0 



80 



.56 



.59 



70.7 



11.5 



70 



.42 



.43 



Feb. . . 



1 



74.0 



8.2 



82 



.60 



.63 



78.7 



12.7 



74 



.44 



.49 





2 



74.0 



7.3 



86 



.64 



.70 



77-8 



11.6 



77 



.48 



.54 





3 



74.3 



6.0 



87 



.70 



.72 



76.6 



10.2 



76 



.52 



.52 



Mar.. 



. 1 



83.5 



9.8 



81 



.59 



.59 



89.2 



17.3 



66 



.37 



.43 





2 



82.3 



7.5 



86 



.67 



.68 



86.7 



12.2 



76 



.52 



.52 





3 



79.8 



8.3 



85 



.63 



.66 



83.6 



13.0 



70 



.47 



.44 



April, 



1 



87.5 



6.2 



88 



.75 



' .74 



91.6 



10.8 



79 



.60 



.57 





2 



86.5 



8.8 



84 



.65 



.67 



93.2 



13.8 



75 



.52 



.51 





3 



84.6 



7.6 



86 



.68 



.70 



88.1 



12.7 



75 



.52 



.51 



May, 



. 1 



87.5 



6.1 



91 



.75 



.80 



90.0 



8.2 



86 



.67 



.70 





2 



90.7 



7.9 



86 



.69 



.70 



94.6 



10.9 



80 



.58 



.59 





3 



86.8 



6.5 



89 



.74 



.76 



88.3 



7.5 



86 



.79 



,70 



June, 



. 1 



90.5 



6.4 



88 



.75 



.74 



92.8 



8.1 



82 



.70 



.66 





2 



87.0 



4.8 



91 



.80 



.80 



87.8 



6.1 



90 



.75 



.78 





3 



86.1 



5.6 



87 



.76 



.72 



87.4 



6.9 



85 



.72 



.68 



July, 



. 1 



86.3 



4.0 



91 



.83 



.80 



87.9 



4.6 



90 



.83 



.78 





2 



86.6 



5.1 



91 



.80 



.80 



88.0 



6.0 



90 



.76 



.78 





3 



82.7 



4.0 



88 



.77 



.74 



85.3 



4.8 



88 



.80 



.74 



Aug.. 



1 



85.0 



4.1 



92 



.82 



.82 



86.8 



4.9 



89 



.75 



.76 





2 



85.1 



4.2 



92 



.82 



.82 



86.7 



5.3 



91 



.78 



.80 





3 



84.0 



4.0 



92 



,82 



.82 



85.0 



4.3 



91 



.81 



.80 



Sept.. 



1 



86.3 



4.4 



91 



.76 



.80 



88.3 



5.5 



88 



.82 



.74 





2 



85.9 



4.9 



92 



.75 



.82 



86.4 



5.9 



91 



.76 



.80 





3 



83.7 



4.8 



91 



.80 



.80 



85.0 



6.8 



89 



.71 



.76 



Oct... 



1 



85.2 



5.6 



87 



.76 



.72 



86.8 



7.6 



83 



.69 



.65 





2 



829 



4.0 



83 



.82 



.84 



83.9 



5.0 



91 



.79 



.80 





3 



83.3 



6.8 



87 



.71 



.72 



85.1 



9.3 



82 



.61 



.63 



Nov. . 



1 



79. 



6.9 



84 



.69 



.66 



82.1 



10.1 



77 



.57 



.54 





2 



79.2 



7.5 



85 



.66 



.68 



79.4 



10.1 



78 



.55 



.56 





3 



75.6 



7.7 



85 



.64 



.68 



77.9 



10.0 



79 



.55 



.57 



Dec. 



1 



71.7 



5.8 



85 



.70 



.68 



74.3 



7.2 



82 



.65 



.63 





2 



72.4 



6.1 



87 



.67 



.72 



75.7 



9.0 



81 



.57 



.61 





3 



69.8 



6.1 



84 



.68 



.66 



72.0 



8.9 



78 



.55 



.56 



Means 



81.2 



6.1 



B6.8 



.71 



.72 



83.8 



8.9 



81.5 



.63 



.63 



The actual tension of vapour in inches, found by multiplying Dalton's 

 maximun tension of vapour at t by the percentage here given, is, 



