Meteorological observations and essays / By John Dalton.

  • John Dalton
Date:
1834
Catalogue details

Licence: Public Domain Mark

Credit: Meteorological observations and essays / By John Dalton. Source: Wellcome Collection.

    44/280 (page 18)
    Whatever doubts may be entertained respecting the cause of heat, many of its effects are clearly ascertained: in treating of those effects it is expe- dient to adapt our language to one or other of the suppositions respecting the nature of their cause ; and as nothing has yet appeared to render the common mode of expression unphilosophical, we shall therefore speak of fire as a substance, under the denomination of fire, or heat. One universal effect of fire is its expanding or enlarging those bodies into which it enters ; which bodies subside again when the fire is withdrawn. Solids are least expanded by it ; inelastic fluds, as water, spirits, &c. are more expanded ; and elastic fluids, as air, most of all. Hence, if a glass tube of very small bore, and a large bulb at the end, be filled with any liquid so as it may rise into the stem, and heat be applied to the bulb, the liquor will rise in the tube ; and it is obvious to infer, that the larger the bulb and the smaller the bore of the tube, all other circumstances being the same, the ereater will be the ascent for a given variation of heat: such an instrument, when applied to a frame properly graduated, is called a ¢hermometer. Dit- ferent fluids have been occasionally used for ther- mometers, but none is found to answer so well, in all respects, as quicksilver. Boiling water is of a constant and uniform tem- perature at all times and places, provided the barometer be at a certain height ; and a mixture of pounded ice, or snow, and water is likewise of a