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PHYSICS OF THE GLOBE.
By CLEVELAND ABBE,
INTERNAL CONDITION. The remarkable address of Sir William Thomson at the Glasgow meeting of the B. A. A. S. in 1876, in which he renounced the views so long entertained by him as to the internal fluidity of the earth, and gave in his adherence to Hopkins's conclusion as to its solidity, has been followed by a paper by Gen. J. G. Barnard, in which he differs from some of the points taken by Thomson.
INTERNAL TEMPERATURE. In reference to temperatures observed deep within the earth, Mr. Oswald Foster has communicated to the Cambridge Philosophical Society a memoir in which he maintains that the abnormal temperatures observed in the artesian well 4000 feet deep at Sperenberg might be accounted for by vertical currents, while the average rate of increase is 1° Fahr. for every sixty feet of descent.
The very delicate and exact and convenient method of observing temperatures at points underground, or otherwise of difficult access, by means of the so-called electro-thermometer, as used by Becquerel at Paris, deserves to be introduced at some of the physical laboratories of America. Observations have been made daily for many years at Paris, the results of which have lately been communicated to the Academy of Sciences.
VOLCANOES. Of general work on vulcanicity we make especial mention of the investigations of Mr. G. K. Gilbert, of Powell's Geological Survey of the Western Territories, who by the study of peculiar formations among the Henry Mountains, of Utah, has revealed an entirely new type of volcanic eruption, in which the lavas, instead of finding vent at the surface of the ground, ceased to rise while still several thousands of feet under ground, and lifted the superincumbent strata so as to make for themselves deep-seated subterranean reservoirs, within which they congealed, to be revealed only after the erosions of subsequent ages. The volcanoes of Iceland have been investigated by Professor Johnstrup, whose report is published by the Danish government.
EARTHQUAKES. A violent earthquake occurred at 8.30 P.M. May 9th on the southern coast of Bolivia and Peru, destroying many small towns. It was central near Iquique, and was accompanied by an oceanic wave about sixty-five feet high at the central stations. This wave reached San Luis Obispo and Honolulu simultaneously at about 5 A.M. of the 10th (Honolulu time), doing much damage in the Sandwich Islands, where much activity had been previously observed in the volcanoes (see Monthly Weather Review, May; Am. Journal of Science; and Petermann's Mittheilungen, Dec. 1877).
A new electric seismograph of much completeness has been invented by Secchi. Some such instrument is much to be desired for use on our Pacific coast.
TERRESTRIAL MAGNETISM. An interesting memoir is published by Wijkander on magnetic perturbations and their connection with the aurora borealis. This is mainly an historical introduction to the important observations published by the Swedish expedition to Spitzbergen in 1872-73. The connection was first noted by Celsius and Hjorter (1741) in Sweden, at whose request Graham (1761), in England, made corresponding observations, so that the simultaneity of the phenomena was at once revealed. The Swedish expedition has established the fact that the magnetic disturbances which attend an aurora have their origin, or act as if they originated, at points on a zone that extends from British America northeast to North Cape and then around the globe, apparently not far from the zone of greatest auroral frequency as established by Loomis or Fritz. The cause of these disturbances is to be looked for in the existence of abnormal electric currents produced near the earth's surface by some change in atmospheric conditions. These disturbances are themselves subject to daily and annual fluctuations; they are of a general and of a local nature, and can be detected instantly by simultaneous observations at several distant and several neighboring stations. The connection between the aurora and these disturbances in the magnetic instruments is of a secondary nature to the connection between the latter and the telluric electric currents. Since the lesser magnetic disturbances are almost continually occurring, the traces of aurora are also almost as frequent. (This agrees with the inference fairly deducible from the numerous auroras recorded in the Monthly Weather Reviews of the Army Signal Office.)
The magnetic survey of Russia during 1871–75 by J. Smirnow has been published in a translation from the original Russian. Smirnow gives a comparison with Sabine's charts, and shows where observations are now or soon will be most needed.
Hann contributes an instructive review and comparison of the diurnal and annual periods in the magnetic declination at Russian and Australian stations.
“The Absolute Direction and Intensity of the Earth's Magnetic Force at Bombay, and its Secular and Annual Variations,” by Ch. Chambers, gives the result of magnetic observations at Bombay since 1867. The magnetic elements are all progressing in the positive direction.
The Coast Survey Report for 1874, published during this year, contains valuable memoirs by Schott on secular change of magnetic declination in the United States, and a discussion of the results of the self-recording instruments at Key West, 1860–1866.
EARTH CURRENTS. At a recent social meeting of the London Society of Telegraph Engineers, Mr. Saunders, of the Eastern Telegraph Company, exhibited some diagrams showing some results of simultaneous observations of the earth currents observed at both ends of the broken cable between Suez and Aden. A striking coincidence is seen between the currents observed on the two sections of the cable.
DENSITY, ETC. Mohn contributes to Petermann's Mittheilungen a memoir on the temperature of the Atlantic east of Greenland. He shows that a belt of warm water extends northeastward to beyond the North Cape. This belt moves eastward in summer and westward in winter. He also accurately defines the limits of the bottom stratum of cold water at maximum density, and shows how it is limited by the configuration of the sea bottom.
Schmidt, of Dorpat, has extended his memoir on the salinity of natural waters to the ocean and salt seas, and in a comprehensive table gives the results of all known observations.
TIDES. The tidal observations made by the English Polar Expedition of 1876 have been reduced by Professor Haughton, and in a preliminary account of his results read before the British Association, he stated that the results obtained by Dr. Bessels from the Polaris expedition were confirmed by the English expedition, viz., that there was a junction of two important tides in the largest portion of Smith's Sound. A new type of tide had been found confirming Dr. Bessels' reasoning to show that Greenland is an island.
At the same meeting of the B. A. A. S., papers “ On the Tides of Port Louis and of Freemantle were read by Sir William Thomson, and “On Solutions of Laplace's Tidal Equation for certain Special Types of Oscillation.”
WAVES. Forel, of Morges, on the north shore of Lake Geneva, has from the study of the self-recording tide-gauge of large scale shown that the surface of the lake oscillates rhythmically in fixed periods about two axes, i. e., the longest and shortest diameters of the lake. The times of vibration are respectively seventy and ten minutes.
Numerous notices have appeared in the Monthly Weather Review of remarkable fluctuations in the waters of our Great Lakes. These, however, appear mostly to be due to earthquakes, and have as yet never been shown to have any such
regularity as Forel finds for Lake Geneva, although possibly such may be revealed by self-recording instruments.
The oscillograph is the name given by Bertin to an apparatus for recording continuously the rolling and pitching of a vessel at sea. The apparatus has been lately extensively used in the French navy, and affords important data both for ship-builders and for students of wave motion. It is also applicable to the determination of that correction to an anemometer record on shipboard needed in order to obtain the correct velocity of the wind at sea.
An important paper on the progression of waves was read by Osborne Reynolds at the Plymouth meeting of the B. A. A. S., and an equally important one by Lord Rayleigh on the same subject was presented to the Mathematical Society in November,
INTRODUCTORY. The following brief notice of the scientific activity of the year in the department of meteorology brings our record down to the last of December; and, however imperfect it may be, yet suffices to show that but few preceding years have been marked by more important events. Among these latter we would place the extension of the United States network of meteorological observers over the elevated regions west of the plains of the north west and south west, the extension of its system of international simultaneous observations to the vessels of the United States Navy and the United States, British, and German merchant marine; the publication of several volumes by the new India Meteorological Office under Blanford; the works of Brault on the winds of the Atlantic; those of Guldberg and Mohn on the mechanical laws that pervade the cyclonic and anticyclonio areas of wind and pressure; and the elegant memoir of Ferrel on the general circulation of the atmosphere, with accompanying polar charts of isotherms and isobars.
INSTITUTIONS AND PERSONS. The Army Signal Office, although somewhat hindered by a diminution of its quota of men, has continued its labors