That a remedial tincture of rock-crystal could be made was firmly believed by the Danish chemist, Ole Borch (Olaus Borrichius, 1626–1690), and in his chemical lectures he gives the following directions as to the processes to be employed. A rock-crystal was to be heated to a high temperature and then cast, while still warm, into cold water; it would thereupon break up into small fragments. By heating these particles together with tartaric salts, the whole mass would be reduced to a liquid solution. Half of the quantity, after cooling off, was to be put into a distilling glass with the best “spirit of wine” and was to be digested in a bath of lukewarm water. It would then be seen that the solution became red. This process is repeated several times, and finally the tincture is concentrated by distilling off the spirit of wine, leaving the pure rock-crystal tincture. Its remedial quality is stated to have been applicable to dropsy, scrofula, or hypochondriac melancholia, if it were taken in doses up to forty drops in a proper medium.[313] [Illustration: ANCIENT PERSIAN RELIC KNOWN AS THE “CUP OF CHOSROES” The engraved rock-crystal medallion in the centre depicts Khusrau II, Parwiz (A. D. 591–628), in the peculiar and characteristic garb of the Sassanian monarchs. The strange wing-like adornments rising from each shoulder, and the moon crescent and sun-disk above the head, are especially noteworthy. In the Royal Museum, Bucharest, Roumania. ] To make the _magisterium_ of rock-crystal, a pound of the substance was to be heated to a high temperature and then dipped into spirits of vitriol. After this operation had been repeated ten times, the rock-crystal was to be ground, on a marble slab, to a very fine powder, which was a sure remedy for gout and for calculi formed in any of the bodily organs. The spirits of vitriol in which the rock-crystal had been dipped was sometimes filtered through blotting-paper and sold as crystal spirits of vitriol; this was asserted to be a powerful diuretic, from seven to ten drops being given at a dose in a cup of meat broth.[314] As late as the last half of the eighteenth century a Dr. Bourgeois recommended the use of rock-crystal, calcined and ground, as a very excellent astringent in the most obstinate cases of diarrhœa. In reporting this, Valmont de Bomare (1731–1807) adds that it would be desirable to know the nature of the acid in rock-crystal and its state of combination.[315] Here, as in all cases where some of the constituents of precious stones may really possess certain curative powers, a better result can be attained by using these constituents in other forms or combinations.