Many of the well-waters contain gases; thus the town of Roma is lighted by natural gas which escapes from its well.
Travers, The Study of Gases (1901).
Stomata are often absent, absorption and excretion of gases in solution being carried on through the epidermal layer.
Trans., 18 53, p. 357, 18 54, p. 321, and 1862, p. 579) showed that the statement that no internal work is done when a gas expands or contracts is not quite true, but the amount is very small in the cases of those gases which, like oxygen, hydrogen and nitrogen, can only be liquefied by intense cold and pressure.
This phenomenon is connected with the fact that incandescent bodies, especially in rarefied gases, throw off or emit electrons or gaseous negative ions.