The object of this paper was to show the true character of storms, illustrated by those of 2d, 3d, and 4th December 1863. It was pointed out that the mode usually adopted of laying down the isobarometric lines was calculated to present an erroneous view of their figure or form. The laying down representative lines in round numbers of 5 millemetres in each, or in two-tenths of an inch of barometric readings, lead deceptively to the conclusion that the areas of least pressure were circular or elliptical.

It was then shown that the lines of equal pressures were ribbed into the latitudinal line of minimum barometer, which was usually found running north and south, sometimes nearly straight, but often curved, with its convex side towards the east. The minimum line of barometer was easily fixed by consulting the self-registering barometers. The minimum line of barometer was shown to have been on the meridian of London at 8 a.m. of the 3d December, and apparently nearly straight from Algiers to the Orkney Islands.