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cnlng and working of the glass in the flame of a lamp,in the use of which Caflius was very conversant: that theaddition of nitre and sal ammoniac calls forth the colour,and that the colour produced by sal ammoniac is morebeautiful than that by nitre, but quickly disappears on acontinuance of the fire.

Orfchal, in a treatise entitled solsne vejle , gives a pro-cess, by which he fays he obtained a very fine ruby. Hedirects the purple precipitate, made by tin, to be groundwith six times its quantity of Venice glass in very finepowder, and this compound to be exquisitely mingled withthe fritt or vitreous composition to be tinged : his frittconsists of equal parts of borax, nitre, and fixt alkalinefait, and four times as much calcined flint as of each ofthe salts ; but in what proportion the gold precipitate isto be mixed with the fritt, and in what manner the fusionis to be performed, he does not mention. He reportsthat he had found the muddy matter, obtained in polishinggold by a pumice stone, to impart likewise a ruby colourto glass.

Grummet, who had been operator to ICunckel inmaking the red glass, published a tract in opposition bothto him and Orfchal, under the title of sol non sine vese,in which he observes, that the furnace ought to be so con-structed, that the operator may have full liberty of ex-amining the glass in the fire, and of removing it as soonas it appears to have acquired the proper colour : he faysthe enamellers obtain a ruby colour, by melting, with alarge proportion of Venice glass, the brownish powderprecipitated from solution of gold in aqua regia by fixtalkaline salts.. But he imagines that the gold is nowiseconcerned in the production of the colour. Venice glass,and most of the finer colourless kinds of glass, have an ad-dition of manganese, without which it would be very dish-