The Brontometer

Abstract

FOR more than a century meteorologists have been puzzled by the exceptional action of the barometer during some (not all) thunderstorms, and during some (but not all) heavy rains. As a general rule, one expects the barometer to fall for rain and bad weather, but in 1784 Rosenthal pointed out that “when a thunderstorm approaches the place where a barometer is situated, the mercury in the tube begins to rise; the nearer the thunder-cloud comes to the zenith of the observer, the higher does the mercury rise, and reaches its highest point when the storm is at the least distance from the observer. As soon, however, as the cloud has passed the zenith, or has become more distant from the observer, the weight of the atmosphere begins to decrease and the mercury to fall.”