The Garden Guide

Book: Gardening Science - Soils, Manure and the Environment
Chapter: Chapter 4: Weather and Climate

The range of the barometer

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1367. The range of the barometer is considerably less in North America than in the corresponding latitudes of Europe, particularly in Virginia, where it never exceeds 1.1. The range is more considerable at the level of the sea than on mountains; and in the same degree of latitude it is in the inverse ratio of the height of the place above the level of the sea. Cotte composed a table, which has been published in the Journal de Physique, from which it appears extremely probable, that the barometer has an invariable tendency to rise between the morning and the evening, and that this impulse is most considerable from two in the afternoon till nine at night, when the greatest elevation is accomplished; but the elevation at nine differs from that at two by four-twelfths, while that of two varies from the elevation of the morning only by one-twelfth, and that in particular climates the greatest elevation is at two o'clock. The observations of Cotte confirm those of Luke Howard; and from them it is concluded, that the barometer is influenced by some depressing cause at new and full moon, and that some other makes it rise at the quarters. This coincidence is most considerable in fair and calm weather; the depression in the interval between the quarters and conjunctions amounts to one-tenth of an inch, and the rise from the conjunctions to the quarters is to the same amount. The range of this instrument is found to be greater in winter than in summer; for instance, the mean at York, during the months from October to March inclusive, in the year 1774, was 1.42, and in the six summer months 1.016.