Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/444



XIX. Barometrical Measurements.

By WILLIAM ALLEN, F.R.S

[Read 19th November, 1812.]

following measurements were made with a single Barometer of the construction proposed by Sir Henry Englefield, and have been calculated according to the formula recommended by him in his memoir on the subject, which is inserted in the 14th volume of Nicholson's Journal. I shall give in detail the observations made upon Snowdon; and of the other measurements I shall mention only the results.

It appears from observations 1 & 7 that the Barometer had fallen at Beddgelert in 9$$\scriptstyle \frac 12$$ hours 0.09 inches, and from observations 2 & 5 that it had fallen at Llyn Cader in 6$$\scriptstyle \frac 14$$ hours 0.042 inches. The descent of the mercury may therefore be estimated at about 0.008 inches an hour, for which due correction has been made in each observation on calculating the measurements.