Papers on meteorology : relating especially to the climate of Britain, and to the variations of the barometer / by Luke Howard.

  • Howard, Luke, 1772-1864.
Date:
1850-1854
Catalogue details

Licence: Public Domain Mark

Credit: Papers on meteorology : relating especially to the climate of Britain, and to the variations of the barometer / by Luke Howard. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    the scheme which I have given early in this inquiry (second edit. vol. i. p. 5) of the varying mean Temperature of the years, as calculated in great measure to answer this purpose ; it being very clear, that the greatest depth of rain fell in the coldest years, and that the warm years were dry or mean ones. But it will be a great addition to this information, should we be able to prove, from observations now extant, that the Barometer also varies its mean height periodically, from year to year; and that both variations are governed by a periodical succession of the different classes of winds*. “ If the Moon’s attraction be really the principal cause of those variations in the atmosphere which cannot be traced to the influence of the superior planet, the mode of operation of this attraction may be very simple; at the same time that, considering the complicated nature of the Lunar orbit, and the perpetual interference of the Sun’s varying power, its manifestations in any given temperate climate may prove a very difficult subject to investigate. “ On a train of effects, the most part of which are out of the reach of direct obser- vation, we may be permitted, in this part of the work, to hazard a few conjectures. “ The surface of the atmosphere is, I think, less elevated, and better defined, than many persons would be led to imagine it. A portion of air, rarefied by means of the air-pump, does indeed exhibit an elasticity, which seems limited only by the imper- fection of the instrument. Bor the most minute residuum still appears to fill the vessel, and to press against it in all directions. But it does this at a temperature which, compared with that of the extreme boundaries of the atmosphere, is probably as that of the steam in a high-pressure engine to the water in a well. We know that, in ascending in the atmosphere, the temperature is found to decrease with the de- creasing density of the air: and even under a vertical sun, between the Tropics, a line of perpetual snow on the mountains, indicates a boundary within our reach, which the heat never has ascended in mass to penetrate. There is consequently no source from whence air, conveyed to the summit of the atmosphere, could take the heat necessary to such extreme rarefaction ; the whole sensible heat of the atmosphere being derived originally from the earth’s surface, and distributed in an inverse pro- portion to the elevation. At an elevation, therefore, not perhaps on a mean more * The proofs of these positions were adduced by Mr. Howard in five papers communicated to the Royal Society from 1840 to 1845, abstracts of which are inserted in their proper places in the text above, of the preceding and present Sections, and which are given entire in Part II., comprehending all the papers relating to the “ Variations ” and “ Proportions ” of the meteorological elements in question. The subject is alluded to in the “ Cycle of Eighteen Years in the Seasons of Britain,” reprinted in the next Section. See also the paper “ On the Mean Year,” &c. communicated to the British Association in 1844, and noticed further on in the present Section. F \