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542  by means of suitable reagents, which would at the same time color it. These coloring reagents were designated, generally, the philosopher's stone.

Governed by these ideas, the Greco-Egyptian alchemists obtained a great variety of metallic alloys, some white and nearly as unchangeable as silver, to which they assimilated them; others yellow, and having a stability like that of gold, of which they gave them the name. Real gold and silver were besides often included in the composition of these alloys, when they were regarded as the seed, and were supposed to multiply, as if they had been living beings, under the action of certain ferments. The alchemists frequently found that their recipes for transmutation were not sufficient to produce gold and silver; that after combining a certain number of properties, others were still wanting; at this point they fell back upon the mystic part of their science. The confusion between real silver and gold and the white and yellow alloys was carefully nursed by the alchemists, who even went so far as to call gold and silver metals which were only superficially colored by the action of mercury and the sulphurets of arsenic, and metals that were only covered with a golden varnish. This confusion of language exists even in the industries of our own times, as when manufacturers speak of the gold of a color or a cloth.—Translated for the Popular Science Monthly from the Revue des Deux Mondes.



N the summer of 1895 the world lost two men, each of whom, in his own way and in his own country, had exerted an unusual influence on the development of science. They were born and they died within a few months of each other. Each was endowed by Nature with the gift of seeing the relationship of apparently unrelated phenomena; each passed through a medical training; each devoted time, much against his will, to dissection and anatomy; each was a fighter for what he believed true; each was gifted with a winning personality that attracted friends from all sides; each was a great teacher, having a ready sympathy for young students, and each was remarkable for the breadth of his knowledge and the keenness of his insight. One was Thomas H. Huxley, an Englishman, the other Felix Hoppe-Seyler, a German.