restored by a skillful artisan, and it is now supported upon a tripod, the fragments being held together by a band of gold filigree. This remarkable object of antiquity, which is of extraordinary beauty of material and workmanship, furnishes a theme over which the antiquaries love to muse and wrangle. Another of the antique monster emeralds, weighing twenty-nine pounds, was presented to the abbey of Reichenau near Constance by Charlemagne. Beckman has also detected this precious relic to be glass. And probably the great emerald of two pounds weight brought home from the Holy Land by one of the dukes of Austria, and now deposited in the collection at Vienna, is of the same material. The hardness of our glass is yet far inferior to that of the ancients, and even the ruby lustre of the potters of Umbria, which was so precious to the dilettanti of the Cinque Cento period, has not been recovered. The emerald has been a subject of controversy among the chemists and mineralogists, and its character, especially the cause of its beautiful color, is not clearly defined even at the present day. But that distinguished chemist, Professor Lewy of Paris, seems to offer, thus far, the most correct and plausible theory. Ten years ago he boldly asserted that the hue is not due to the oxide of chromium, and with this opinion he confronted such eminent men as Vauquelin, Klaproth and others of high rank in the scientific world. Not content with his researches in his laboratory in Paris, he resolutely crossed the ocean and sought the emerald in its parent ledges in the lofty table-lands of New Granada. Here he obtained new information of a geological character which goes far to strengthen his position. The experiments of M. Lewy indicate, if they do not prove, that the coloring matter of the emerald is organic, and readily destroyed by heat, which would not be the case if it was due to the oxide of chromium. All my own fire-tests with the Granada emerald corroborate the views of M. Lewy, for in every instance the gem lost its hue when submitted to a red heat. Nevertheless, the recent researches of Wöhler and Rose give negative results. These experienced chemists kept an emerald at the temperature of melted copper for an hour, and found that, although the stone had become opaque, the color was not affected. They therefore considered the oxide of chromium to be the coloring agent, without, however, denying the presence of organic matter. The amount of the oxide of chromium found by many chemists varies from one to two per cent., while Lewy and others found it in a quantity so small as to be inappreciable, and too minute to be weighed. Before the ordinary blowpipe the emerald passes rapidly into a whitish vesicular glass, and with borax it forms a fine green glass, while its sub-species, the beryl, changes into a colorless bead: with salt of phosphorus it slowly dissolves, leaving a silicious skeleton.[A]