On the constitution of the atmosphere

Abstract

The object of this paper is to examine the consequences as respects the proportion of the component parts of the atmosphere simultane­ously existing at different heights in one vertical column, which would follow from the atomic theory, on the supposition of a finite number of atoms existing in corporeal bodies, and of such a law of repulsion prevailing among those of elastic fluids, as Sir Isaac Newton appears to have supposed, in which the repulsive power of each par­ticle terminates at the particles immediately adjacent. It is well known that when two or more mutually inactive gaseous fluids are mixed, each distributes itself uniformly through the whole space oc­cupied, and each sustains a part of the whole pressure retaining them, proportioned to its density. This is a necessary consequence of the mutual inelasticity and independence of the gaseous atmospheres with respect to each other. Each exerts the whole mechanical force its quantity will allow, without regard to the others; and the sum of all these forces in the state of equilibrium counterbalances the total pressure. This uniformity of density, however, is only a consequence of the assumed principle, where the gases occupy such small spaces as we can command in our experiments, in which the total pressure may be regarded as uniform, in a vertical as well as in a horizontal direction; it is otherwise when we regard a column of indefinite height, or one prolonged to the limit of the atmosphere, —a limit at which the weight of a single particle is in exact equilibrio with the repul­sion between two contiguous ones. It is this case which the author considers in the paper before us. He supposes, for simplicity, two atmospheric columns, one of hydrogen, and the other of carbonic acid, each supporting at its base a pressure of 30 inches of mercury; of such height as to reach to the respective limits of each atmo­sphere, divided each by partitions into cells of equal magnitude, at first insulated from each other, then made to communicate, and finally, the cells to be withdrawn, and a free communication established be­tween every part of the two columns: and from an analysis of what passes in the act of communication, and from the general principles of pneumatic chemistry, he is led to the conclusion, that the arrange­ment of each of the gases in the united column will be precisely the same as if the other had no existence; that is, that each will form a separate and independent atmospheric column, containing at its base a pressure of fifteen inches, and decreasing in density according to its own peculiar law; so that after, a certain height the limit of the carbonic acid atmosphere being passed, hydrogen alone would exist in the column, and after the limit of the hydrogen atmosphere were attained a vacuum.