1826. J Measurement of Heights by One Barometer. 365 



without regard to the altitude. Secondly, the pressure when 

 incorrectly noted at the upper station will introduce errors aug- 

 menting in the ratio of the height (or rather inversely as the 

 pressure observed) ; — errors which increased practice will, how- 

 ever, gradually reduce to insignificant quantities. Thirdly, an 

 improper estimate of the temperature of the air at the summit, 

 although it would vitiate the measurement in the ratio of the 

 height, yet granting the error of observation equal to 3°, its value 

 for an altitude of 10,000 feet would not exceed 65 feet. Lastly, 

 when the decrement of temperature differs from the rate made 

 use of in the construction ot Table VI, the errors will increase 

 as the square of the altitude, and may become in some instances 

 a notable proportion of great elevations. 



I have the honour to be, Gentlemen, 



Your most obedient servant, 



J. Nixon. 



Heights above the Ground Floor of Gearstones Inn. 



Above the Ribble under Norton Bridge. 



Peizer Heights . 

 Moughton Fell. 

 Dubcote Ridge . 



Cam Rakes 



Cash Knot 



Ditto 



Fountain's Fell . 

 •Foxhope Fell, 



Ditto 



Pen-y.gent 



*Ditto 



Ditto 



Ditto 



2 



H 



3 



Above the Wharf under Deepdale Bridge. 



Wharf Head... 



Cam Rakes 



Cam Fell , 



Greenside 



Deepdale Moor . 



Stoke Fell 



DodFeU 



Ditto 



I. 

 I. 



N. 

 N. 

 N. 

 N. 

 N. 

 N. 

 D- 

 N. 

 N. 

 T. 

 D. 



■ • The temperature at the summits (Oct. 25, 1825) was steadily at 33® from 10a.m. 

 to 4 p. m. ; but on reaching their common middle base, 400 feet lower, the thermometer 

 rose on numerous trials to 38°, 39°, and 40° ! 



