420 



Experimental Researches on the Depressions [July, 



Barom. 

 pres- 

 sure 

 inches. 



Ascend 

 Temp 

 of air. 



ing series. 

 Wet- Wet- 

 bulb, bulb. 



1 2 



Descending 

 Wet Wet- 

 bulb, bulb. 



3 4 



series. 

 Temp, 

 of air. 



a . i 



'<n.S I 



>-< 3 1 

 P-.CD 1 



PS 



a ao 

 .9 S 

 & s 



Cu'-f 



Mean 



depres- 

 sion ob- 

 served . 



Calcu- 

 lated 

 depres- 

 sion. 30 



dXP 





» 



o o 











• 





30 



92.7 



S0.4 82.0 resetted) 



80.5 





93.0 



11.7 



13.0 



12 



12. 



28 





79.7 80.8 



79.2 







12.6 



14.3 



13.1 



12.9 



26 



92.9 



78.0 80.0 rewetted 



76.8 



79.2 





13.9 



15-5 



14.6" 



14.0 



24 





77.8 



74.7 



75.2 





15.0 



18.0 



17.0 



15.0 



22 



92.7 



75.4 (re wetted 



72.4 



73.8 





16.4, 20.4 



19.1 



16.4 



20 





73.0 





70.2 





19.8| 23.3 



21.5 



18.0 



18 





70.3 





66.9 





22.5! 26.6 



24.5 



20.0 



16 





67.7 





64.2 





24.2] 29.3 



26.8 



22.5 



14 



93.0 



64.0 





61.2 





29. | 32.3 



30.6 



35.7 



12 





60.0 





57.4 





33. 36.1 



34.5 



20.0 



10 





54.9 (rewetted 



54.6 



53.8 



93.2 



38.1 39.7 



38.9 



36.0 



8 





48.3 



47.3 





93.2 



44.7 



45.9 



45.3 



45.0 



6 





38.0 



38.8 





92.5 



55.0 



53.7 



53.1 



60.0 



5 





31.0 



30.8 





91.6 



62.0 



60.8 



61.4 



72.0 



4.4 





rewetted 



23.7 





89.S 





66.1 



1 66.1 



81.3 



At the first glance towards the final columns of this table, one might 

 at first be led to exclaim, upon the wonderful accordance between theo- 

 ry and fact ! The ascending series, especially, agrees exactly with the 

 calculation in several points, and does not diverge materially until the 

 pressure falls to six inches, far beyond the reach of any likely contin- 

 gency within our observance. 



But all this seemingly agreeable coincidence is, in a measure, delusory. 

 The effect is compounded of two different influences — 1 , the rarefac- 

 tion ; and 2, the diminution of humidity which is consequent thereon. 

 We know from our second section of experiments how to appreciate 

 this latter disturbing cause, and so isolate the reduction of tempera- 

 ture due to the diminished pressure alone ; but the prior experiments 

 give us an opportunity of estimating it in a more direct manner. 

 Thus, taking experiment 7, we have the following data : the temper- 

 ature being 91°. Fahrenheit. The fourth column contains the hypo- 

 thetical depressions on the supposition of the inverse-pressure ratio. 



Barometrical 



Depression 



Increment 



Theoretical 



Increment 



Calculat- 



pressure 



in dry air. 



observed. 



depression. 



d+ 3 l-d 

 P 



ed co-effi- 



inches. 



D 



D — d 



dxlL 



cient. 





O 



A 



p 



8 



A-t-S 



30.0 



32.7 





32.7 







27.5 



35.6 



+ 2.9 



43.6 



+ 10.9 



.27 



15.0 



42.3 



-f 9.6 



65.4 



+ 32.7 



.29 



7.5 



61.0 



+ 28.3 



130.8 



+ 98.1 



.29 



6.0 



70.8 



+ 30.1 



165.5 



-f- 132.8 



.23 



5.5 



72.1 



H- 39.4 



176.5 



+ H3.8 



.27 



5.4 



72.8 



-f 40.1 



179.8 



+ 147.1 



.27 



The rate of increment observed, it will be remarked, here invariably 

 falls short of the calculated rate in the fifth column, but it bears al- 

 ways the same proportion to it, about one-third ; as shewn in the 

 sixth column : therefore in this example the law of the inverse pres- 

 sures holds good relatively, but it requires a co- efficient to reduce the 

 absolute amount. Thus, the maximum depression in dry air at any 



