397 
of mountains in the north of England. 
plumb lines. And here I must mention how greatly we were 
favoured by the weather : the sun only shone during the first 
observation, and it was nearly a calm during the whole of 
the measurement, so that Airey could frequently, by inserting 
the pole a little in the ground, set it on a balance, which 
would remain during the time necessary for adjusting the 
level, and observing it. 
I have also to observe, that we chose so precipitous a 
descent, that the pole was seldom 40 feet from the telescope, 
therefore no allowance was necessary for the earth's curva- 
ture. 
I found the most expeditious and exact mode of managing 
the pole, was to stop Mr. Airey, when I perceived its top to 
be about an inch above the cross wires ; as I could then make 
signs to him to press it into the earth by little and little till the 
coincidence was exact : the telescope was then carried down 
to the pole, and placed (when levelled) in exact correspon- 
dence with the zero. The pole was again removed down to a 
new station, and this mode continued till we had compleated 
six observations, or 50 yards of descent. Here the barometer 
was again set up, separately examined as before; and this 
process continued to the foot of the mountain. 
After descending 175 yards, it was necessary to take a 
dead level of half a mile, which was corrected by several 
observations back and forward, as also by a middle station. 
We measured 400 yards down the first day, and on the 
following day compleated 900 yards, which brought us to the 
village of Applethwaite, and near the level of Bristow Hill, 
about a mile distant. 
The next day many observations were made back and 
