a minute investigation both of the rocks and simple minerals had never been yet instituted, and the arrangement and examination of the high land, the most conspicuous and extensive part of the isle, till remained a field quite unexplored.
The grotesque and unfaithful attempt of Fannin to lay down the mountains in his map of the island published in 1789, can hardly be considered as an improvement upon the much earlier and rough sketches of Collins, Durham and Speed.
From the materials and documents which I collected when in the Isle of Man, I have since my return from Ireland constructed a map chiefly expressive of the features and appearances of the mountainous tract, which I now present to the Society; acknowledging at the same time the able and kind assistance afforded me by Mr. Webster, draughtsman to the Society.
The height of Snei-feldt was a long time ago determined by means of the barometer, by Bishop Wilson, and it has been since
- This map however is neither complete nor as perfect as I wish I had been able to execute it. Mr. Wm. Geneste (a gentleman of Douglass, to whom I am much indebted) has had the complaisance to undertake last Summer at my request, a trigonometrical survey of the Isle of Man, conjointly with Mr. James Kewley, a person who has formerly practised as a Surveyor. But I fear the result of their labours, which Mr. W. G. intended with a great liberality to put at my disposal, will not be ready to be published in this volume of the Transactions of the Geological Society.
- The height of Snafield (says the Bishop) as taken by an exact barometer, is about live hundred and eighty yards, the mercury subsiding two inches and one tenth. Vol. I. p. 449.
This is very probably the first application that was made of the barometer in Great Britain to determine the elevation of a mountain. The original experiment pointed out by Pascal, was performed by Perier (his brother in-law) on the “ Puy de Dome,” 19th Sept. 1648. Bishop Wilson came over to the Isle of Man in April 1698, where during his long residence, he made the experiment that led him to the elevation of Snei-feldt.