Aqueous Vapour Atmosphere. 107 
racy of the barometrical variation between 
the valley of Wythburn at the foot, and the 
summit of the mountain. From the road at 
the Nag’s Head public house to the top of 
the mountain the barometer falls usually in 
the month of July 2.62 inches: it has never | 
with me been less than 2.58 nor more than 
2.68, whatever was the state of the atmos- 
phere as to pressure and temperature. 
From barometrical results I calculate the 
height of the road at the foot of the mountain 
to be 180 yards above the level of the sea: 
also the summit ‘of the mountain to be 850 
or 860 yards above the road, making a total 
of 1035 yards perpendicular elevation above 
the sea. 
On the opposite side of the valley to the 
west is a parallel range of mountains, about 
a mile distant, and half the height of the 
Helvellyn range; beyond these are other 
mountains, but of no great altitude, till the 
distance of eight or ten miles, when they are 
again high. 'The east side of Helvellyn from 
the summit a considerable way down is ex- 
ceedingly steep, so that the summit is scarcely 
accessible on that side; beyond, the moun- 
tains gradually fall to an extensive plain. 
The usual mode of my operations was to 
find a spring on the side of the mountain ; 
