The Cause of Cyclones

IN the winter of 1922–23 there appeared in NATURE some correspondence on “The Cause of Anticyclones,” and on that occasion I put forward certain views as to the mechanism by which the more rapid increases of barometric pressure are brought about in temperate latitudes (NATURE of March 31, 1923, pp. 429–430). The present communication may be regarded as a sequel in that its object is to describe a mechanism by means of which the more rapid reductions of pressure can conceivably be produced. The idea arises naturally from consideration of a series of papers by Helmholz appearing in the Sitzungs-berichte of the Royal Prussian Academy of Sciences in 1888 and 1889, dealing with the equilibrium of rotating rings of air at different temperatures, and with the theory of winds and waves where strata of different density lie contiguous with one another.