Volume 1

The climate of London, deduced from meteorological observations, made in the Metropolis, and at various places around it / by Luke Howard.

  • Howard, Luke, 1772-1864.
Date:
1833
Catalogue details

Licence: Public Domain Mark

Credit: The climate of London, deduced from meteorological observations, made in the Metropolis, and at various places around it / by Luke Howard. Source: Wellcome Collection.

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    hours, or a longer period, extending to a week if desirable, but re¬ gulated by the season of the year, the water being returned into the measure, the quantity which is evaporated may be read off, and the vessel replenished. For warmer Climates, or longer pe¬ riods of observation, the depth of the vessel may be increased, and a greater number of measures put in. See fig. p. xvii. Where the Evaporation alone is in question, and the observer wishes to ascertain it daily, without trouble, the following con¬ trivance may be used. On a Plate of glass, six inches long, and an inch and a half w ide, a line is to be drawn, near and paral¬ lel to one side, to serve for a base. From this a diagonal Scale, etched with fluoric acid, is to be carried up, ascending at the rate of one inch in ten; so that the tenths of an inch into which it is ultimately divided, shall rise in progression just one hundredth part of an inch above each other. The glass being now fixed perpen¬ dicularly on its edge, in a vessel of the proper capacity and depth, (if this be square it may be set in diagonally, and supported by the angles,) a little Water is first to be put in ; the surface of which is to be brought, by adjusting the position of the vessel, to range with the horizontal line at the bottom of the scale. This adjust¬ ment made, more water is to be added, up to the line which cuts the division at Zero. Then, in proportion as the surface is low¬ ered by evaporation, it will cut the several divisions in succession, indicating at sight the effect to the hundredth part of an inch. 11 have varied the position of the Scale in this instrument, and made it an inclined plane. A piece of plate glass, about eleven inches long, by an inch wide, is graduated in the manner of a measuring rule, in divisions one tenth of an inch apart, which are numbered at every ten, from 0 to 100. The dividing lines being half