Page:Popular Science Monthly Volume 27.djvu/147

Rh has not had an opportunity to investigate his hypothesis, but he makes a few statements that illustrate how apparently small this potential may be. "To raise a single pound of water," he says, "in the form of vapor from the sea or from moist ground, requires an amount of work equal to that of a horse for about half an hour. This is given out again, in the form of heat, by the vapor when it condenses; and the pound of water, falling as rain, would cover a square foot of ground to the depth of rather less than one fifth of an inch. Thus, a fifth of an inch of rain represents a horse-power for half an hour on every square foot; or on a square mile, about a million horse-power for fourteen hours. A million horses would barely have standing-room on a square mile. Considerations like this show that we can account for the most violent hurricanes by the energy set free by the mere condensation of vapor required for the concomitant rain. Now, the modern kinetic theory of gases shows that the particles of water vapor are so small that there are somewhere about three hundred millions of millions of them in a single cubic inch of saturated steam at ordinary atmospheric pressure. This corresponds to or so of a cubic inch of water—i. e., to about an average rain-drop. But if each of the vapor particles had been by any cause electrified to one and the same potential, and all could be made to unite, the potential of the rain-drop formed from them would be fifty million million times greater. Thus it appears that if there be any cause which would give each particle of vapor an electric potential, even if that potential were far smaller than any that can be indicated by our most delicate electrometers, the aggregation of those particles into rain-drops would easily explain the charge of the most formidable thundercloud."

How an Iron-Ore Bed was formed.—Professor James P. Kimball, of Lehigh University, has published in a single pamphlet two papers on the iron-ores of the Juragua Hills, of the province of Santiago, Cuba, beds of a hematite or specular ore, which appears to be largely the result of the weathering of the highly basic rock which gives the geological character of the formation. These rocks, the eruptive material which gave origin to the iron-ore, consisted of proto-silicates, or silica combined with the protoxide bases, iron, lime, and magnesia, and with alumina. Under its new conditions at and near the surface, with access to oxygen in the atmosphere, circulating waters, etc., the protoxide of iron became rapidly further oxidized into ferric or sesquioxide, which is a comparatively stable product under conditions prevailing at the surface. The oxidation of the ferrous to ferric oxide is attended with more or less complete dismemberment of the eruptive rock, little by little. Silica originally combined with the ferrous oxide is isolated as silica. Silicates of lime, magnesia, and alumina form new aggregates among themselves. Soluble matter as fast as isolated enters into solution in circulating waters, and is thus at hand to assist in the work of weathering. This work of alteration has gone on until a complete change has been wrought not only in the composition but also in the arrangement of the original eruptive rock. By the law of molecular attraction a process of concentration has gone on simultaneously with the process of weathering decay. Homogeneous material, such as ferric oxide, was collected by itself to a degree far greater than the other earthy residues, because, in the process of conversion from ferrous to ferric oxide, it has been in solution, and so in circulation, and has hence become finally deposited under long-prevailing conditions of uniform circulation. The process here briefly followed out has gone on just below the surface, within the range of the circulating waters. The same action immediately at the surface is followed by waste or diffusion of the products of alteration. In the present case, the best of the ore-bodies are mainly, if not indeed wholly, replacements of coralline limestone.

Jules Verne as a Scientific Authority.—The "Revue Scientifique" discusses a curious question in giving its estimate of the value of Jules Verne as a scientific writer. It considers the judgment, which many of us are ready to give, that such science as is inserted into the framework of a romance is worse than no science at all, as too severe.