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don must be fastened a cross-piece, by means of wliich the whole may be kept always vertical. A steel magnet is provided with a square slit, such that it can be placed any where and in any position upon the parallelopipedon. According, then, as certain co-efficients in the expression for the magnetic disturbance are larger or smaller, the magnet is to be placed either parallel or transverse to the parallelopipedon, and is to be moved up or down until the needle points accurately north and south, when the magnet is to be fastened in that position. The ship is then to be swung, and a third magnet is also to be fastened to the same parallelopipedon in a certain manner described by Garbich, until when the ship heads east and west the needle still points correctly worth and south, when this third magnet is to be fastened in its place. With this adjustment the correction of the compass is finished, except in so far as there may still remain a slight error, due to the want of symmetry in the apparatus, and which may be corrected by swinging the ship to the west as well as to the east. In order to compensate for the remain. ing rolling or heeling deviation, a cylindrical steel magnet, about seven inches long and two thirds of an inch thick, is appropriate, which is to be placed before the needle and inclined to the vertical, at an angle whose tangent is a wellknown co-efficient. This compensation becomes of great importance in high latitudes. In passing into magnetic southern latitudes, the vertical compensating magnet must be reversed end for end. The easiest method of directing the ship toward any given point of the horizon will be attained by the use of a compass described by Garbich, combining in itself both magnetic and azimuthal compass, having three concentric azimuthal circles, and which is to be used in connection with the azimuthal tables computed by Labrosse, which give, for every latitude of the ship and every position of the sun, and for every hour of the day between sunrise and sunset, the angle between the meridian and the sun's vertical. -"Mittheilungen” Austr. Ilydrog. Office, 1874, 167, 257, 426.
ANCIENT MUSICAL INSTRUMENT IN CHINA.
Among the ancient musical instruments of the Chinese is the pien king, which is an assortment of sixteen stones arranged on strings in two series of eight each, one above the other, and each giving out, when struck successively, the system of sounds employed by the ancient Chinese in their music. The size and shape of these stones have been very carefully determined by them after a minute analysis of the sounds peculiar to each one. In order to render the sound graver, the thickness of the stone is diminished to the proper amount, and, to render it more acute, something is cut off from the length. The stones thus arranged remind one in effect of a series of steel bars, as exhibited in acoustic apparatus to illustrate the fact that vibrations above a certain pitch are inaudible to the human ear. Frequent endeavors have been made to decide what kind of stones were employed in the fabrication of the pien king, since they were customarily paid as tribute money more than two thousand years before Christ by certain provinces of China. Certain authors have thought that they recognized in them a kind of black marble; and the editor of the works of Father Amiote asserts that the king, or musical stone, constructed in France from the black marble of Flanders, was quite as sonorous as those of China. Lately a discovery was made at Kendal, in England, of some musical stones, which, when struck with a piece of iron or another stone, gave out sounds of very different pitch, and with eight of which it would be possible to attain a very distinct octave.-13 B, III., 203.
REMARKABLE IMPROVEMENTS IN STRINGED INSTRUMENTS.
Some very remarkable results of persistent investigation have been just communicated to the Physical Society of London by Mr. Hamilton, of Oxford. In prosecuting these researches Mr. Hamilton has for over two years resigned all other work, and he announces finally that, by means of stringed instruments reinforced by reeds, he has been able to secure for these all the advantages of organ pipes, in addition to those which they already possessed. In short, the strings vibrating on the sounding-board are made to imitate exactly in volume, quality, and sustained sound either an open diapason pipe or the largest organ pipe in use, his hearers being satisfied that not only can a string do all the work of an organ pipe in volume and sweetness, but also afford the exquisite sympathetic and blending power hitherto considered to be peculiar to strings. Another invention of his is a string which, to the great surprise of those who attempted it, could not be put out of tune. Mr. Hamilton is still engaged in perfecting his inventions, which promise to give us the effect of an organ in a piano-forte, and that of a pianoforte in a cottage instrument. -12 A, XI., 99.
HARMONY IN MUSICAL INSTRUMENTS. In a course of lectures on the science of music Mr. Ellis has explained the defects of the ordinary keyed instruments, toned by a system which he characterizes as the worst possible, in that every element of harmony is violated. In the piano-forte the errors of temperament are not so offensive as in the organ and in the harmonium. In olden times organs were tuned on a temperament which put the principal keys in good tune, but more recently organists, having made up their minds to play in all sorts of remote keys, a great change has taken place, and an equal temperament has been attempted. For show organs this course may be defended, but not for church organs, where nothing but the simplest keys are required. The organ of half a century ago was a sweet-sounding instrument compared with the harsh ones of modern days. A curious proof occurred a few years ago of the mischief done to the tone of an organ by the equal temperament. Dr. Pola had to construct two organs of tolerable size. In the one he gave way to popular prejudice by having it tuned equally; in the other he adopted the old tuning; and though the instruments were precisely alike in other respects and made by the same builder, the latter organ acquired the reputation of being peculiarly sweet-toned, while the former was considered harsh.-12 A, XI., 89.
D. CHEMISTRY AND METALLURGY.
VANADIUM IN ROCKS. Vanadium, hitherto regarded as one of the rarest metals, is now said by Dr. A. A. Hayes to be very widely diffused. It occurs as vanadic acid, associated with phosphoric acid, in minute traces in very many of our commonest rocks. In fact, it seems to be almost as frequently met with as manganese. Dr. Hayes has detected it in green and plum colored slates and porphyries, in sandstones, and in various rock aggregates.-1 A, April 16, 1875, 166.
CRYSTALLIZED CADMIUM. Hermann Kämmerer has obtained fine crystals of metallic cadmium by distilling the metal in a current of hydrogen in a combustion tube. These crystals were silver white, and seemed to belong to the regular system, there being regular octahedrons, dodecahedrons, and other more complicated forms. The experiment can be performed in the lectureroom before a class.-21 A, May, 425.
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OXIDATION OF RUTHENIUM. Ruthenium, the rarest metal of the platinum group, differs from its associates in the ease with which it undergoes oxidation. Its properties in this respect have recently been investigated by Deville and Debray, who worked chiefly with the tetroxide, RuOg. This substance is easily formed by the fusion of ruthenium before the oxyhydrogen blowpipe. The metal then oxidizes almost as readily as antimony, giving off a blackish vapor which smells strongly of ozone. Strangely enough, however, the oxide, although formed at such a high temperature, can not be heated without decomposition. By simply heating a specimen of it to about 108° Centigrade, it can be made to decompose with a very violent explosion, yielding a large quantity of highly ozonized oxygen. These peculiarities seem to distinguish it from all other known oxides.-Annales de Chimie et de Physique, April, 537.
Although the compounds of barium have been so long and so thoroughly known, the metal itself has been but little studied. Sergius Kern, of St. Petersburg, has lately succeeded in preparing it by several methods in a state suitable for examination. The best process seems to be to heat barium iodide with metallic sodium. A violent reaction ensues, accompanied by an evolution of heat and light; the resulting mass is treated with mercury to form a barium amalgam, from which, finally, the mercury is distilled. The barium so obtained resembles calcium very closely, is apparently tough and ductile, and has a specific gravity of 3.75.-1 A, June 4, 243.
PURIFICATION OF TIN BY FILTRATION. Curter has proposed an interesting method of freeing tin from less fusible metals by means of filtration. The filter was constructed as follows: Common tinned iron of ordinary thickness was cut into strips about 150 millimeters long by 100 wide. Five hundred of these, with their sorfaces parallel, were wedged together in an oblong iron frame, and this frame was tightly fitted into an opening in the bottom of a large graphite crucible. The tin to be purified was then melted in another crucible, and allowed to cool until crystals began to form on its surface, when it was transferred to the above-described filter. Of course the heat sufficed to melt the tinning of the iron strips, thus leaving narrow spaces between them through which the molten metal could flow, its solid impurities remaining behind. More than fifty centners of impure Bohemian tin was thus rendered almost chemically pure, the iron, copper, and arsenic with which it had been contaminated being left, alloyed with some of the tin itself, upon the filter.-14 C, March, 469.
THE ARTIFICIAL IMITATION OF NATIVE MAGNETIC PLATINUM.
It is known that occasional pieces of native platinum not only act upon the magnetic needle, but are themselves mag. netic, like the true iron magnets. Berzelius and Kokscharof have contributed somewhat to our knowledge of the chemical and other properties of this platinum, and have shown that there is always a certain quantity of iron associated in