The corona formed again at nine; and, though again broken, was imperfectly visible after that time. At half past nine, the eastern portion of the sky became tinted with intense red and green; but at half past ten, little else remained than the appearance of bright horizontal beams of a white colour in the north. If it be admitted that the centre of the aurora was precisely midway between a Aquila and a Lyræ, at twenty minutes past eight, its azimuth must have been 1° 14′ 42′′ E. of S., and its altitude 73° 27′ 6′′; the latitude of the observer being 40° 20′ 47′′ N. The point thus designated, would be very nearly in the direction of the dipping needle; the dip being, by observation, 72° 47' 6" (72° 47.1') and the variation (though not accurately determined,) some 4° W. or that of the S. end of the needle, of course, the same extent to the east. The degrees of azimuth, reckoned on a parallel to the horizon at an altitude of 72° and more, being small, the deviation from the direction of the dipping needle, measured on the arc of a great circle, would be scarcely more than 1° towards the N. W. Professor Bache stated that his own observations near Philadelphia, of the altitude of the apparent converging point of the auroral beams, at nine, P. M. made it but about 69°. He had witnessed a case of the appearance of a dark spot of irregular shape, between two beams of light, which was certainly not a cloud, as the stars were not at all obscured by it, and which he supposed to be the phenomenon referred to recently by Professor Lloyd. No mottled clouds, such as usually attend the aurora, were visible during the period between nine and ten o'clock, when he had been able to observe. Professor Bache stated that he did not place much stress upon his measurements, as he had been prevented from sustained observation by indisposition. There had been, in the newspapers, an account of an auroral display visible at London, on the morning of the fourth of September, at about the same absolute time as at Princeton, according to Professor Alexander's observations. It was said to have been accompanied by a very unusual number of shooting stars, compared in one statement to the splendid display of November 13th, 1833. Professor Henry had examined the light of this aurora by the polariscopes of Savart and Arago, but had not been able to detect the slightest trace of polarization. The following extract from a letter, addressed by Professor Henry, of Princeton, to Professor Bache, was read, announc ing the discovery of two distinct kinds of dynamic induction, by a galvanic current. "Since the publication of my last paper, I have received through the kindness of Dr. Faraday, a copy of his fourteenth series of experimental researches; and in this I was surprised to find a statement directly in opposition to one of the principal results given in my paper. It is stated in substance, in the 59th paragraph of my last communication to the American Philosophical Society, that when a plate of metal is interposed between a galvanic current and a conductor, the secondary shock is neutralized. Dr. Faraday finds, on the contrary, under apparently the same circumstances, that no effect is produced by the interposition of the metal. As the fact mentioned forms a very important part of my paper, and is connected with nearly all the phenomena described subsequently to it, I was anxious to investigate the cause of the discrepancy between the results obtained by Dr. Faraday and those found by myself. My experiments were on such a scale, and the results so decided, that there could be no room for doubt as to their character; a secondary current of such intensity as to paralize the arms having been so neutralized, by the interposition of a plate and riband of metal, as not to be perceptible through the tongue. I was led by a little reflection to conclude that there might exist a case of induction similar to that of magnetism, in which no neutralization would take place; and I thought it possible that Dr. Faraday's results might have been derived from this. I have now, however, found a solution to the difficulty in the remarkable fact, that an electrical current from a galvanic battery exerts two distinct kinds of dynamic induction: one of these produces, by means of a helix of long wire, intense secondary shocks at the moment of breaking the contact, and feeble shocks at the moment of making the contact. This kind of induction is capable, also, of being neutralized by the interposition of a plate of metal between the two conductors. The other kind of induction is produced at the same time from the same arrangement, and does not give shocks, but affects the needle of the galvanometer; it is of equal energy at the moment of making contact, and of breaking contact, and is not affected by the introduction of a plate of copper or zinc between the conductors.* The phenomena produced by the first * Since writing the account of the two kinds of induction, I have found that the second kind, although not screened by a plate of copper or zinc, is affected by the introduction of a plate of iron. In the cases of the first kind of induction, iron acts as any other metal. kind of induction form the subject of my last paper as well as that of the one before; while it would appear from the arrangement of Dr. Faraday's experiments, that the results detailed in his first series, and those in the fourteenth, were principally produced by the second kind of induction. Although I may be too sanguine in reference to the results of this discovery, yet I cannot refrain from adding that it appears to lead to a separation of the electrical induction of a galvanic current from the magnetical, and that it is a step of some importance towards a more precise knowledge of the phenomena of magneto-elec tricity." Dr. Bache announced the death of William Sullivan, Esq., late a member of the Society, and Dr. Hare was requested to prepare an obituary notice of the deceased. The following gentlemen were duly elected members of the Society: THOMAS U. WALTER, of Philadelphia. JOHN PENINGTON, of Philadelphia. EUGENE A. VAIL, of Paris. CHARLES RUMKER, of Hamburgh. CHARLES GUTZLAFF, of Macao. JOHN WASHINGTON, Captain R. B. N. ELIAS LOOMIS, of the Western Reserve College, Ohio. Mr. DU PONCEAU, President, in the Chair. The following donations were received: FOR THE LIBRARY. Astronomical Observations, made at the Royal Observatory, Edinburgh. By Thomas Henderson, F.R.S.E., &c. Vol. II. For the year 1836. Edinburgh, 1839.-From the Royal Society of London. Nieuwe Verhandelingen der Eerste Klasse van het Koninklijk- Journal of the Convention of the State of Pennsylvania, to propose A Reports on the Ichthyology and Herpetology of Massachusetts. By D. Humphreys Storer, M. D.-From the Author. Carte Générale de l'Empire d'Allemagne, par M. Chauchard. Paris, 1791. From Mr. Du Ponceau. Carte de la Partie Septentrionale de l'Italie, par M. Chauchard. Paris, 1791. From the same. Renati Descartes Principia Philosophiæ. Amsterdam, 1692.-From Mr. William Kintzing. Friderici Wilhelmi Pestel Commentarii de Republicâ Batavâ. Ley. den, 1782.-From Mr. John Vaughan. Meteorological Essays and Observations. By J. Frederic Daniell, F.R.S. London, 1827.-From the same. New Remedies: the Method of preparing and administering them; their Effects on the healthy and diseased Economy, &c. By Robley Dunglison, M. D. Philadelphia, 1839.-From the Author. The Select Medical Library. Six Volumes. Philadelphia, 1838 and 1839. From the Editor. The Eclectic Journal of Medicine. Edited by John Bell, M. D. Vol. III. Philadelphia, 1839.-From the Editor. The American Journal of Science and Arts. Conducted by Benja min Silliman, M. D., LL. D., aided by Benjamin Silliman, jr., A.B. Vol. XXXVII. Nos. 1 and 2. For July and October. New Haven, 1839.-From the Conductors. A letter was read from the Secretary of the Geographical Society of Paris, announcing the purpose of that society to form a Geographical Museum, and inviting contributions from the members of this society. The Committee, consisting of Dr. Bache, Dr. Patterson and Mr. Booth, to whom the paper of Doctor Hare, read at the last meeting of the society, was referred, entitled, "Description of an Apparatus for deflagrating carburets, phosphurets, or cyanides, in vacuo, or in an atmosphere of hydrogen, between electrodes of charcoal; with an account of the results obtained by these and other means, especially the isolation of calcium, and formation of a new fulminating compound. By R. Hare, M. D., Professor of Chemistry in the University of Pennsylvania," reported in favour of publication in the Society's Transactions. The publication was ordered accordingly. |