Abnormal Variations of Barometric Pressure in the Tropics, and their Relation to Sun-Spots, Rainfall, and Famines

Abstract

IN the first part of his work on the Meteorology of the Bombay Presidency, which was submitted to Government in August, 1875, Mr. Charles Chambers pointed out that the variation of the yearly mean barometric pressure at Bombay shows a periodicity nearly corresponding in duration with the decennial sun-spot period (see “Meteorology of the Bombay Presidency,” § 26, p. 12), and in August, 1878, in a letter to NATURE, vol. xviii. p. 567, I drew special attention to this relation, pointing out that the observations of the winter and summer half-years, separately as well as conjointly, show that the pressure is low when the sunspot area is great, and vice versâ, but that the pressure curve lags behind the sun-spot curve.