Page:Popular Science Monthly Volume 32.djvu/234

222 At most, lead and zinc are susceptible of being converted into oxide or carbonate in a moist medium; but under such conditions they are disintegrated and fall into dust, while the tablet is quite compact and covered with a very fine and extremely clear inscription. Its real nature was therefore a riddle. We then first carefully sounded it, and ascertained that there was no central metallic leaf in its thickness. Chemical analysis indicated that it was a pure, crystallized carbonate of magnesia—a substance that is more refractory to dilute acids and atmospheric agencies than carbonate of lime. The polishing of the tablet appeared to have been completed with the aid of an almost insensible trace of fatty matter, which manifested itself on calcination. We observe here that our magnesia and its salts were not known in antiquity and the middle ages, and that pure and crystallized carbonate of magnesia is a very rare mineral, and was not known by Haüy at the beginning of the present century. But in intimate association with carbonate of lime it constitutes dolomite, a very abundant rock. Carbonate of magnesia is found principally in veins intercalated in talcose schists, serpentine, and other magnesian silicates, where it results from the slow decomposition of the rocks by natural agencies. The material of the tablet in question also includes a few traces of silica, which indicate the same origin. The choice of so exceptional a mineral for the fabrication of a sacred tablet can not have been made by chance. It doubtless responded to some particular religious idea. At any rate, it proves that the Assyrians were acquainted with the carbonate of magnesia as a proper substance. To what word did this tablet correspond in the inscription, in which it appears to figure under the name of one of the supposed metals? Notwithstanding the absence of a special denomination on this tablet, M. Oppert believes that it was designated by the word a-bar, which had been supposed to mean tin. I thought it might be useful, in the effort to obtain new light in this matter, to analyze the substance of which the great bulls in the Louvre Museum are made, and see if it contained dolomite. The analysis determined, however, that this matter was a crystallized carbonate of lime representing the physical constitution of marble, or rather of that variety of limestone which was formerly confounded, under the name of alabaster, with anhydrous sulphate of lime.

While I was studying the tablets of Khorsabad, M. Heuzey called my attention to some metallic fragments of a vase and a votive figurine which came from M. de Sarzec's excavations at Tello. The fragment represents a portion of a cylindrical circular band which formed the mouth of a cast vase, and had been prepared by melting and casting. A part of the throat that separated this band from the body of the vase proper can still be seen. It is very simple in form, and without any inscription or even light delineation. The surface is covered with a very thin, yellowish-black patina. The mass is formed of a brilliant black metal, the fracture of which exhibits