METEOROLOOICA L OBSER VA TIONS. 
363 
place^ as if they had been very roughly read.* Never- 
theless the aneroid readings have been of use as checks 
on the barometer and hypsometers, and also when those 
instruments were not observed, for indicating the approxi- 
mate pressure required for calculating the dew-point. 
The heights have mainly been deduced from the ba- 
rometer, using the hypsometer's indications when it was 
not observed. In the few cases where the heights depend 
upon the aneroid, the readings have been approximately 
corrected by the latest comparison with the barometer, 
always reducing the reaching of the latter to 32° F. 
The heights deduced can only be regarded as approxi- 
mations or estimations, because simultaneous observations 
at a lower station of reference, as a base line, could not be 
procured. They might, however, be obtained from some of 
the observatories in the north of India. Even then the 
frequent absence of the actual temperature of the air, at 
the place and time of observation, would prevent an accu- 
rate determination of the height. 
It has been necessary therefore to resort to average 
values for pressure and temperature, determined at a lower 
station. The observations taken at Roorkee, latitude 
29° 52^ N., longitude 77° 57' E., 880 feet above the sea, 
during the years 1865-8, appeared to be the most suitable 
that could be obtained ; but these were only for pressure, as 
follows : — 
Months. Barometer at 32° F. 
May 28-762 inches 
Jane 28-625 
July 28-638 „ 
August 28-696 
September 28-779 „ 
October 28-969 „ 
November 29-109 „ 
Vide Buchan on Mean Pressure of the Atmosphere in 
Edin. Phil. Trans, vol. xxv. 
* Even with the aid of a lens, thei^e aneroids could not be read more 
correctly, as the scale extended from thirty-one inches down to fourteen and 
eleven. ^G. H.'] 
