Summary—An account is given of recordings of vertical electric currents in the atmosphere from November, 1938, to August, 1939. General results are given and some special phenomena analysed in detail.
The measurement of the electric charge on rain is of interest from two points of view; in the first place, the precipitation‐currents may be of importance in the discussion of what Wormell [see 23 of “References” at end of paper] has called “the electrical balance sheet of the Earth”; and further, the results for the charges on rain can give clues as to the mechanism involved in the acquisition of such charges and hence as to the processes at work in producing separation of charge in and below clouds.Measurements in various parts of the world have shown that there is a positive excess of charge brought down to the Earth, more especially in rain classified as “continuous,” “ordinary,” or “non‐stormy” (German “Landregen”). Apart from this, little has been achieved in the establishment of general results capable of providing a basis for theoretical discussion.
Observations for specific conductivity of the atmosphere and the detection of the presence of radio‐active emanations were taken, in accordance with the Director's instructions, on the portions of the cruise between Falmouth and Madeira, Madeira and Bermuda, and Bermuda and New York. The plan was to devote alternate days to conductivity and radio‐activity observations. This program was interfered with by bad weather and by the failure on some occasions of the Zamboni dry pile which was used to charge the collecting wire in the radio‐activity experiments.I. Conductivity Observations.
That terrestrial latitudes vary with an average period of 428 days seems now to be an established fact. In other words, the pole of figure of the Earth is known to be moving continuously around its pole of rotation in the direction of decreasing west longitudes at a mean rate of one complete circuit in 428 days (ignoring for our present purpose the corresponding annual motion of the pole of figure). For each position of the pole of figure a set of stresses must be produced in the Earth representing its tendency to assume a new figure,—a new ellipsoid of revolution with its axis of figure coincident with the axis of revolution. These stresses are doubtless partially relieved, and only partially, by actual movements of matter to new positions in the oceans, in the envelope of atmosphere, and perhaps in the so‐called rigid Earth. Even with this partial relief each portion of the Earth is subjected to periodic stresses which repeat their various phases every 428 days. This suggests that there may possibly be corresponding periodic variations in the elements of terrestrial magnetism produced by these stresses.
1. This article is based on my three unpublished investigations on the distribution of the inclination,21 of the declination,26 and of the horizontal intensity27 over Siberia, and is published in somewhat different form in Russian.30 The publication of the Russian abstract, instead of the three quoted articles in extenso, was necessitated on the one hand by my proposal of a magnetic survey of Siberia,29 and by the desirability of having data on the distribution of terrestrial magnetism over Siberia in connection with the actual conclusion of the general magnetic survey of the globe by the Department of Terrestrial Magnetism of the Carnegie Institution of Washington on the other hand. If Asiatic Russia, which covers over a ninth part of the land area of the globe, occupies the last place in the list of the large continental countries as concerns magnetic surveys, this defect can partly be compensated for by summaries of all determinations of the magnetic elements thus far made and by theoretical investigations based on the results obtained. The paucity of distribution of magnetic stations over even such easily accessible parts of Siberia as the provinces of Akmolinsk and Semipalatonsk was shown by me in a special paper with its accompanying chart.8
IV. VARIATION WITH ALTITUDE OF FALL OF POTENTIAL.That the Earth possesses a negative charge is shown by the generally positive fall of potential. Whether there exist also in the air electric charges, and, if so, whether they be positive or negative, can not be decided by observations made at the surface of the Earth; for this purpose observations in the upper regions alone suffice. If we premise a uniform distribution in the air of the charges in question along horizontal layers, then, in the absence of a charge of the air of its own, the fall of potential should remain constant for the same altitude; in the case of a positive charging of the air the fall of potential must decrease, and for a negative charge, the same should increase. I, therefore, some time ago pointed out the importance of such measurements, and have shown how it would be possible to carry them out in a balloon without conduction with the Earth. Parenthetically it may be remarked, that similar observations on high mountains, on account of the disturbances in the equipotential planes, can not replace, for this purpose, the balloon observations.
[In order to make accessible Passalskij's memorable treatise1 to the readers of the Journal, who are unfamiliar with the Russian language, Prof. Paul Wernicke, working under the auspices of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, has translated the portions of chief interest, the first installment of which is given in the present number. For a biographical sketch of the author and a brief résumé of the contents of Passalskij's work, see Professor Leyst's article, this Journal, Vol. VII, pp. 67–74. The author during his all‐too brief life, he having died November 25, 1900, at the age of twenty‐nine years, evinced unusual talents, a tireless industry and an unbounded enthusiasm for magnetic work.—ED.]
Abstract 297.J Let the components of the current at any point be u, v,w. Let the components of the electromotive intensity be X, Y, Z. The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if Vis the potential,
Abstract There are hree classes in which we may place different substances in relation to the passage of electricity through them. Thehe first class contains all the metals and their alloys, some sulphurets, and other compounds containing metals, to which we must add carbon in the form of gas-coke, and selenium in the crystalline form.
Abstract The discovery by Örsted of the magnetic action of an electric current led by a direct process of reasoning to that of magnetization by electric currents, and of the mechanical action between electric currents. It was not, however, till 1831 that Faraday, who had been for some time endeavouring to produce electric currents by magnetic or electric action, discovered the conditions of magneto-electric induction. The method which Faraday employed in his researches consisted in a constant appeal to experiment as a means of testing the truth of his ideas, and a constant cultivation of ideas under the direct influence of experiment. In his published researches we find these ideas expressed in language which is all the better fitted for a nascent science, because it is somewhat alien from the style of physicists who have been accustomed to establish mathematical forms of thought.