If we rate at 50° Fahr. the mean annual heat in the Isle of Man, we shall have it differing from that of London merely by 1° for a difference of 2°,41′ of north latitude. Comparing the same annual heat of the Isle of Man with that of Edinburgh, we shall find it surpassing the latter by 2°,2′ Fahr. though the latitude of the Isle of Man be only 1°,45′ more to the south than that of Edinburgh.
The mean temperature of the month of June, 1811, in the Isle of Man, deduced from 128 thermometrical observations, I found to be 55°,81′ Fahr. but as most of the observations were made on the tops of mountains, the mean must be lower than it would have been had the observations been made in the plain. Thus I find that thirty-nine thermometrical observations (out of the series of 128) made by the sea side give for the mean 57°,37′, which when compared to the mean of 22 thermometrical observations made at the apartments of the Royal Society on corresponding days, is deficient by 4°,35′. The London mean being 61°,72′, and that of the Isle of Man 57°.37′. At Belfast the mean is 64°,90′ Fahr. The mean height of the barometer for the same month of June, 1811, is as follows.
|Isle of Man||30.11895|
The frosts are short in the Isle of Man, and the Snow does not lie long on the ground, especially near to the sea. I was informed by the Rev. Mr. William Fitz Simmons, that on the top of Sneifeldt it does not remain longer than two or three weeks, from Christmas generally, to the second or third week of January.