on the Formula for measuring Heights by the Barometer . 235 
3. Correction for the elongation of the atmospherical column 
by humidity. 
1 , -/+■/ , -607 + -453 
■*" 6 + B— (/+/')“ + 28-395 + 25-712 — (-607 + .452) ~ 
= 1 +S§8= 1 ' 01996 - 
4. Correction for the pressure of atmospherical vapour, 
g f =28-395 —'^2= 28-395 — -101 = 28-294 
6 ~6 
1 f r ./LKO 
B — g j =25-696 — -^-=25-696 — 075 = 25-621 
And log. m=.lo, 28-294— log. 25 621 = -043098 
Fathoms. Feet. 
Hence h= 1 0,000 x 1 0781 1x1 01 998 x -043098 = 473*9 = 2843*4. 
This result exceeds the height, as deduced by trigonometrical 
measurement, by 12 feet ; but, if the temperature of the mer- 
cury in the barometer, at the upper station, be taken at a mean 
between the temperature of the attached and detached thermo- 
meters in the tent (and there seems to be no reason why the 
former should be preferred to the latter), the corrected altitude 
of the mercurial column, at the upper station, would be 25*704, 
and being corrected for the pressure of the vapour, 25*629. 
The calculation being repeated with this result, the height would 
be found 2826*8, which is about 4^ feet less than the geometri- 
cal height. By the method of De Luc, the result is 56 feet less 
than the truth ; but, by the formula of Sir George Shuckburgh 
and General Roy, it exceeds it by 13-4 feet, a proof of the cor- 
rectness of that formula, when the air is in a mean state of hu- 
midity. 
In another set of observations which were made by Sir George 
Shuckburgh, on Mount Saleve, when the wind was SW., and 
the weather hazy, accompanied with thunder, the following re- 
sults were obtained : 
Bar. Att. Therm. Det. Therm. 
Lower station, 28.390 71°.6 73° 
Upper station, 25.702 73 A 64 
In this case, the point of deposition cannot, on account of the 
humid state of the atmosphere, be estimated to be more than 4° 
