90 Daniell on the Correction 



the state of the vapour must be regulated by the state of the 

 general temperature, and its density will be governed by its 

 more rapid decrease. It is sufficient for our present purpose to 

 have ascertained that in both cases the constituent temperature 

 of vapour tends to a gradual though very different decrease by 

 equal differences, as we ascend through equal spaces, and the 

 general law of nature favours equality of change throughout the 

 whole of any given column of the atmosphere. 



To this, as well as to the general law of the diminution of 

 heat in ascending in the atmosphere, we may apply the obser- 

 vation of Professor Play fair. "This law is subject to certain 

 anomalies, both annual and diurnal; and those intermixed with 

 other accidental irregularities, which it would be difficult, per- 

 haps impossible, to ascertain. All that can be said of it is, 

 that it is the law which nature tends to observe, and that the 

 sum of the deviations from it on the one side is probably equal 

 to the sum of those on the other." — Edinburgh Phil. Trans. ; 

 vol. i. (1788.) 



It will be matter for future investigation, to ascertain more 

 accurately in what manner the two principles modify each 

 other; for there can be little doubt but that the presence of 

 vapour influences the gradations of heat as much as the latter 

 obviously regulates the former. 



I shall now conclude this paper by supposing a case in which 

 all the proper observations have been made for the purpose of 

 shewing more distinctly the manner in which I propose to apply 

 the table of correction. 



Barom. at lower station 29.528 Temp, of mercury, 58° 



upper station 28.161 51i 



Correct for density of 29.528 



mercury 084 



29.444 Log. .4689378 



Do. Do. 28.161 

 - .060 

 28.101 Log. .4487063 



Approximate height in fathoms 202.315 



X 6 



Do. Do. in feet 1213.890 



