Page:Transactions of the Provincial Medical and Surgical Association, volume 4.djvu/205

 Rh The scale has been duly affixed after several accurate measurements from the ivory point.

In the following tables of barometrical heights, every correction has been applied, except that for the elevation of the village, so that they are strictly comparable one with another: in the Royal Society's barometer, the variable correction for capacity—and in the barometer at Malvern, the constant one, .055 has been added for capillary action; the diameter of the bore in the latter instrument being so much smaller than in the former, renders this requisite. The whole of the heights stated have been reduced to one temperature, 32°F.

That the reader may be put in possession of the practical application of these corrections we shall subjoin the detail of the process, taking the mean height of the barometer for September 1834 in London and Malvern.

In order to make a comparison between two barometers absolutely accurate, it is necessary that the elasticity of the vapour of the atmosphere should he estimated at each place, by determining the dew-point, and adding or subtracting according as it is higher or lower in the one place or the other.—This would be a very laborious task; and as the correction is always small, it has been neglected. I have made the correction for the means of the different seasons hereafter stated, and I find the difference between the barometer in London and Malvern to be, for the summer quarter, only .007 in., and for the autumn .016 in.