Hydrostatics and pneumatics / [Dionysius Lardner].

  • Dionysius Lardner
Date:
1831
Catalogue details

Licence: Public Domain Mark

Credit: Hydrostatics and pneumatics / [Dionysius Lardner]. Source: Wellcome Collection.

    353/376 (page 337)
    The most obvious contrivance which is suggested by these considerations is atmospheric air rarefied by heat; for in this case, the expansion produced by the heat gives the same degree of elasticity with a much less quantity of atmospheric air. To explain this, let a glass bulb A be furnished with a tube T, which, rising from it to the extremity at which it is curved, descends into a vessel V, jig. 47., containing water or other liquid : the air is thus enclosed in the tube in the common state of the external atmosphere. Let a spirit lamp, or any other source of heat, be now applied to the bulb at A ; Fig. 47. the air in the bulb receiving increased elasticity from the heat will press the water towards the mouth of the tube, and, rising in bubbles, will escape at the surface of the water. This will continue until the air in the tube is highly rarefied; still, however, retaining a degree of elasticity sufficient to balance the atmospheric pres- sure acting on the surface of the water in the vessel, and transmitted by it. to the surface of the water in the tube. That the air in the tube is highly rarefied, may be verified by removing the lamp from the bulb: as the tube cools, the air will contract itself into its former dimensions, and the pressure of the atmosphere will z