Observations and Reports (continued). London:-Nautical Almanac Office. Local Particulars of the Total The Observatory. No. 8. 8vo. Washington 1895. North American Fauna. Weather Bureau. Maryland State Weather Service Monthly Journals. The Bureau. Boletin de Minas Industria y Construcciones. Año XI. Num. 2, 3. 4to. Lima 1895. Horological Journal. June, 1895. 8vo. London. Escuela de Ingenieros, Lima. British Horological Institute. The Selborne Society. Nature Notes. June, 1895. 8vo. London. Physical Review (The). Vol. II. No. 6. 8vo. New York 1895. The Editors. Beddard (F. E.), F.R.S. A Monograph of the Order of Oligochaeta. The Author. Part II. Sixth The Author. Biologia Centrali The Authors. Harley (V.) The Normal Absorption of Fat, and the Effect of Extirpation of the Pancreas on it. 8vo. [Cambridge] 1895. The Author. Helmholtz (H. von), For. Mem. R.S. Handbuch der Physiologischen Optik. Zweite Auflage. Lief. 11. 8vo. Leipzig 1895. The Publisher. Preston (T.) The Theory of Light. Second edition. 8vo. London February, 1895. Folio. Lewes 1895. Reid (C.) On Scottish Inter-Glacial Deposits. 1895; [and 2 other Excerpts]. 8vo. 8vo. The Author. [London] The Author. Rockhill (W. W.) Diary of a Journey through Mongolia and Tibet in 1891 and 1892. 8vo. Washington 1894. Smithsonian Institution, Washington. Schück (A.) Magnetische Beobachtungen an der Deutschen Bucht der Nordsee. 1894. 8vo. Hamburg 1895. The Author. June 20, 1895. The LORD KELVIN, D.C.L., LL.D., President, in the Chair. Mr. J. Wolfe Barry, Professor A. G. Bourne, Professor J. R. Green, Mr. E. H. Griffiths, Mr. C. T. Heycock, Professor S. J. Hickson, Major Holden, Prof. W. MacEwen, Dr. S. Martin, Professor G. M. Minchin, and Mr. W. H. Power were admitted into the Society. A List of the Presents received was laid on the table, and thanks ordered for them. The following Papers were read: I. "On the Magnetical Results of the Voyage of H.M.S. 'Penguin,' 1890-93." By E. W. CREAK, Captain R.N., F.R.S. Received May 8, 1895. (Abstract.) In view of the numerous magnetic surveys of different countries which have been made in recent years, it seems important to call attention to the increasing value of magnetic surveys made over that much larger area of the earth, the sea; the coasts washed by the sea; magnetic disturbances proceeding from land under the sea, and the settlement of the question of the direction of the iso-magnetics when passing from deep water to the land. The magnitude of the subject is self evident, therefore it is presumed that under existing circumstances of paucity of information, any well conducted series of observations of the kind required will be welcomed. H.M. surveying ship "Penguin" being ordered to survey the West Coast of Australia, proceeding there by way of the Suez Canal, it was decided to equip that vessel with the necessary absolute magnetic instruments for observations on land and other necessary instruments for relative observations on board the ship. The "Penguin" being practically an iron ship, general observations of the magnetic elements at sea were not undertaken, but the special attention of the observing officers was directed to obtaining the following observations: (1.) The magnetic elements on land at all ports visited. (2.) Local magnetic disturbances on islands. (3.) The magnetic survey of the West Coast of Australia, which, until the "Meda's" observations in 1885-86, was a terra incognita as far as the inclination and force were concerned. (4.) The position and extent of an area of remarkable local magnetic disturbance, reported by H.M. surveying vessel "Meda " as situated under the sea at Port Walcott (N.W. Australia) and two miles from the visible land. With regard to (1)-A series of observations with the absolute instruments were made at twenty-three different places situated on the route from Malta, via Australia, to Hong Kong. These are shown in Table I. At For (2)-Observations of local magnetic disturbance on land were made at Perim Island and Baudin Island (N. Australia). Perim the principal disturbance was found in the inclination, being about 10 to 2° in value. At Baudin Island, the declination was disturbed 540, the inclination 230. Horizontal force undisturbed. For (3)—The magnetic elements were observed at twelve stations between King George's Sound and Baudin Island. With regard to (4), the chief interest lies in the area of disturbance termed a magnetic shoal," from its situation at 9 fathoms below the sea level. Four days were devoted to the survey of this shoal, whilst observations were being made on the neighbouring land. (Data contained in Tables III and IV.) This survey was necessarily carried out on board the ship with the relative instruments. The results were the mapping of an area of magnetical disturbance 34 miles long by 13 miles average width, extending in a north-easterly direction. The positions of the greatest easterly disturbance and westerly disturbance having been found in proximity to one another, the ship was moored in the neighbourhood, and observations of declination, inclination, and total force made. From these a sectional plan of the magnetic rock causing the disturbance has been made, and, together with the complete set of observations, the following results have been deduced. The cause of the disturbance is a ridge of rock permanently magnetized, repelling the north-seeking end of the needle. In the transverse section this ridge is steeper on the south-east side where the disturbances are at a maximum than on the north-west side. Longitudinally the ridge rises rather abruptly to a principal peak (as determined by the point of maximum disturbance of the vertical force), followed by a depression, and a second peak, finally falling abruptly to the level. The principal values of the disturbances caused by this ridge are— 56° E. on S.E. side, 26° W. on N.W. side. -29°. Declination.... .... Inclination Vertical force ... -1.92 on S.E. side; +1.04 on N.W. side. -444 metric units. A geological survey of the coast at the Red Cliff (see map), where the greatest disturbances of the magnetic elements were observed, was made, and specimens of rock and sand were obtained which have since been tested for susceptibility. The evidence from these does not give any direct information tending to show the exact nature of the rock causing the remarkable disturbances over the magnetic shoal, but the character of the disturbances caused by the visible and invisible land are of a similar character. Five diagrams are appended showing the data from which the foregoing results have been deduced, with a map showing the position of the "magnetic shoal" relative to the neighbouring land. Also a geological map of the Red Cliff and neighbourhood. II." A Dynamical Theory of the Electric and Luminiferous Medium. Part II; Theory of Electrons." By JOSEPH LARMOR, F.R.S., Fellow of St. John's College, Cambridge. Received May 16, 1895. (Abstract.) In a previous paper on this subject,* it has been shown that by means of a rotationally elastic æther, which otherwise behaves as a perfect fluid, a concrete realization of MacCullagh's optical theory can be obtained, and that the same medium affords a complete representation of electromotive phenomena in the theory of electricity. The ponderomotive electric forcives were, on the other hand, deduced *Roy. Soc. Proc.,' November, 1893; 'Phil. Trans.,' 1894, A, pp. 719-822. from the principle of energy, as the work of the surplus energy in the field, the motions of the bodies in the field being thus supposed slow compared with radiation. It was seen that in order to obtain the correct sign for the electrodynamic forcives between current systems, we are precluded from taking a current to be simply a vortex ring in the fluid æther; but that this difficulty is removed by taking a current to be produced by the convection of electrons or elementary electric charges through the free æther, thus making the current effectively a vortex of a type whose strength can be altered by induction from neighbouring currents. An electron occurs naturally in the theory as a centre or nucleus of rotational strain, which can have a permanent existence in the rotationally elastic æther, in the same sense as a vortex ring can have a permanent existence in the ordinary perfect fluid of theoretical hydrodynamics. In the present paper a further development of the theory of electrons is made. As a preliminary, the consequences, as regards ponderomotive forces, of treating an element of current ds as a separate dynamical entity, which were indicated in the previous paper, are here more fully considered. It is maintained that a hypothesis of this kind would lead to an internal stress in a conductor carrying a current, in addition to the forcive of Ampère which acts on each element of the conductor at right angles to its length. Though this stress is self-equilibrating as regards the conductor as a whole, yet when the conductor is a liquid, such as mercury, it will involve a change of fluid pressure which ought to be of the same order of magnitude as the amperean forcive, and therefore capable of detection whenever the latter is easily observed. Experiments made by Professors FitzGerald and Lodge on this subject have yielded purely negative results, so that there is ground for the conclusion that the ordinary current-element ds cannot be legitimately employed in framing a dynamical theory. This result is entirely confirmed when we work out the properties of the field of currents, considered as produced by the convection of electrons. There can be no doubt that a single electron may be correctly taken as an independent element of the medium for dynamical purposes; so that electrodynamical relations deduced from a statistical theory of moving electrons will rest on a much surer basis than those derived from the use of a hypothetical current-element of the ordinary kind, in cases where they are in discrepancy. Now it is shown that an intrinsic singularity in the ether, of the form of an electron e, moving with velocity (x, y, ż) relative to the quiescent mass of ather, is subject to a force e (P, Q, R), given by equations of the form Pcj-bż-dF/dt — dvdx; VOL. LVIII. |