The United States Government is, or has been, establishing a meridian line at Springfield, partly to make observations on this coming eclipse, and with the further view of determining a standard of surveyed lines—all of the Government surveys in Illinois having been geodetic. Professor Austin, of the Smithsonian Institute, is in charge of the work, aided by an able corps of assistants.
Diamond-Cutting.
At the Great Exhibition in Paris, in a part of the park contiguous to the Netherland section, M. Coster, of Amsterdam, has erected a building wherein all the processes of diamond-cutting are carried on.
The first rough shaping of the more important facets of the brilliants is here seen performed by the workman, who operates on two diamonds at once, by bruising each against the other, angle against angle. The dust that falls from the stones is preserved for the subsequent processes of grinding and polishing those facets that distinguish the many-sided brilliant from the dull, original crystal of the diamond. It is used, mingled with oil, on a flat iron disk, set revolving with vast rapidity by steam-power, the stone itself being held upon this disk or wheel by a tool to which it is attached by a mass of fusible metallic alloy, into which the stone is skilfully inserted. Skill of eye and hand, only attainable by great practice, is needed for this work; but a skill not less exact is needed for another process, which may here be seen in daily operation—the process of cleavage. The diamond, when a blow is struck on an edged tool placed parallel to one of the octahedral faces of the crystal, readily splits in that direction. But to recognize the precise direction on the complex and generally rounded form of the diamond crystal; to cut a little notch by means of a knife edge of diamonds formed of one of the slices cleaved from a crystal, and to cut that notch exactly the right spot; then to plant the steel knife that is to split the diamond precisely in the right position; finally, with a smart blow, to effect the cleavage so as to separate neither too large nor small a portion of the stone—these various steps in the process need great skill and judgment, and present to the observer the interesting spectacle which a handicraft dependent on experience of hand and eye always affords. But Mr. Coster’s exhibition has other objects of interest. For the first time, we may see here, side by side, the diamond with the minerals that accompany it in the river beds of Brazil; and there are even examples in which crystals of diamonds are included within a mass of quartz crystals, which have all the appearance of having been formed simultaneously with deposits of the diamond.
The different districts of Rio and of Bahia are thus represented—the former producing a confusedly crystallized sort of diamond termed “bort,” and the latter an opaque black variety; both these kinds being found associated with the crystallized diamonds used for jewelry. Though useful in state of powder, the black carbon and “bort” are incapable of being cut as a jewel.—“Maskelyne’s Report,” Great Exhibition.
The Alloys of Aluminum with Copper.
When Sir Humphrey Davy announced the fact that soda, lime, potash, magnesia, and the other alkalies were but oxides of a metallic base, it would have been deemed chimerical to have supposed that the discoveries he made by the expensive aid of the battery would at later date become of really commercial value. He did obtain both sodium and potassium in the metallic state. The substances in this form were new to the chemical world, still more strange to the popular. So new was it to the chemists, that, on a globule of the reduced sodium being presented to a very distinguished chemist, he, with some enthusiasm, examined it; and, admitting the fact of its being a metal, exclaimed, “how heavy it is!”—when the real fact was that its specific gravity was less than water; the expression was the result of the general preconceived opinion that a high specific gravity was a test of a metallic body. It was reserved for a French chemist, Henry St. Claire Deville, to utilize the metal sodium, and that, too, in such a manner that the demand aroused attention to its production;—demand will inevitably bring a supply.
The original reduction was made by Davy, by means of the voltaic battery. After it had been proved that these bases were really metals capable of reduction, chemistry brought all its resources to bear on the problem, and they were produced by other methods than the battery. All the processes adopted, however, were too expensive and laborious, involving an extraordinary amount of complicated manipulations with but inadequate results. The metal sodium, which is the immediate subject of our inquiry, long remained an object simply of curiosity or experiment in the laboratory.