silicon, in several cases going into considerable detail as to the properties of the elements and their compounds. It was in 1875 that the first of these predictions was fulfilled in the discovery of gallium by Lecoq de Boisbaudran. This metal fell in the place which Mendeléeff had given to eka-aluminum, and its specific gravity is 5.9, while 5.8 was the figure which had been foretold. Four years later Nilson discovered eka-boron, and gave to it the name scandium. In 1885 a new silver mineral, argyrodite, was found in the Freiberg mines, and every analysis made of it showed a discrepancy of six or seven per cent. This soon led to the recognition by the analyst, Clemens Winkler, of the presence of a new element, and it further appeared that this new element was Mendeléeff's eka-silicon. Not to be outdone by the French and Swedish chemists, Winkler patriotically called the new metal germanium. It is worth while to show side by side, a few of the predictions of the properties of eka-silicon, published by Mendeléeff in 1872, and the actual properties of germanium, as experimentally determined by Winkler in 1886:
| Eka-Silicon. Symbol, Es. | Germanium. Symbol, Ge. |
| ELEMENT. | |
| Atomic weight, 72. | Atomic weight, 72.3. |
| Specific gravity, 5.5. | Specific gravity, 5.469 at 20°. |
| OXID. | |
| Formula, EsO2. | Formula, GeO2 |
| Specific gravity, 4.7. | Specific gravity, 4. 703 at 18°. |
| CHLORID. | |
| Formula, EsCl4. | Formula, GeCl4. |
| Liquid, boiling a little below 100°. | Liquid, boiling at 86°. |
| Specific gravity, 1.9 at 0°. | Specific gravity, 1.887 at 18°. |
| METALLO-ORGANIC COMPOUND. | |
| Formula, Es (C2H5)4. | Formula, Ge (C2H5)4. |
| Liquid, boiling point, 160°. | Liquid, boiling point, 160°. |
| Specific gravity, 0.96. | Specific gravity, slightly less than water (which is 1.0). |
So close is this agreement that it is difficult to realize that Mendeléeff's forecasts were put in print more than a decade before the element had ever been handled by man.
Since the corrected form of Mendeléeff's table was published in 1871, there has been no end to the speculation upon the subject, and dozens of tables, emphasizing different relations of the elements, have been proposed. Few of these have equaled that of the Russian chemist in simplicity or have as few obscure points. One of these tables, suggested a few years ago by Dr. F. P. Venable, of the University of North Carolina, may be noticed as presenting some decided advantages over that of Mendeléeff:
