Hydrostatics and pneumatics / [Dionysius Lardner].

  • Dionysius Lardner
Date:
1831
Catalogue details

Licence: Public Domain Mark

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

    356/376 (page 340)
    various ascents have since been made, the particulars of which would not be suitable to the limits of the present treatise. The density of each stratum of air being proportional to the pressure under which it is placed, it follows that in ascending in the atmosphere the strata will have less and less specific gravity. A balloon, therefore, contain- ing gas which balances the lower strata, will, if it be completely filled,have a tendency to burst when it has as- cended into the higher strata; for the gas, not having room to expand, will maintain its original elastic force, while the atmospheric pressure being diminished in the ascent will cease to balance this elastic force of the confined gas. There will then be a bursting pressure equivalent to the excess of the atmospheric pressure of the lower strata over the atmospheric pressure in the strata to which the balloon has ascended. These effects may be provided against by imperfectly filling the balloon in the first instance, so that as it ascends, the gas which it contains will have room to ex- pand, and thus, while the pressure of the atmosphere is diminished, the elastic pressure of the gas in the balloon will be diminished in the same proportion. So long as the atmospheric pressure is not diminishecLto that degree which would cause the gas enclosed in the balloon to expand, so as to completely inflate it, no force tending to burst the balloon can exist; but should the ascent be continued to a greater height, then a bursting pressure will be called into action by the pressure of the atmosphere being diminished in a greater degree than the elastic force of the gas in the balloon. In this case the danger may be removed by the provision of a valve opening in some convenient part of the balloon, by which a part of the gas may be allowed to escape. Such a valve is also necessary in order to enable the aeronaut to descend at pleasure. Without it he would be compelled to remain in the atmosphere as long as the balloon continued to retain the gas with which it was inflated; but provided with such a valve, he can allow any portion of the gas to escape, and thereby diminish the magnitude of the bal-