The tincture of cochineal alone yields a purple color, which may be changed to a most beautiful scarlet by adding a solution of tin in aqua-regia, or muriatic acid, a discovery which was made by accident. Cornelius Drebbel, who died in London in 1634, having placed in his window an extract of cochineal, made with boiling water, for the purpose of filling a thermometer, some aqua-regia dropped into it from a phial, broken by accident, which stood above it, and converted the purple dye into a most beautiful scarlet. After some conjectures and experiments, he discovered that the tin by which the window frame was divided into squares had been dissolved by the aqua-regia, and was the cause of the change. Giles Gobelin, a dyer at Paris, used it for dyeing cloth. It became known as Parisian scarlet dye, and rose into such great repute that the populace declared that Gobelin had acquired his art from the devil. _Tyrian Purple._ The purple dye of Tyre was discovered about fifteen centuries before the Christian era, and the art of using it did not become lost until the eleventh century after Christ. It was obtained from two genera of one species of shell-fish, the smaller of which was called _buccinum_, the larger _purpura_, and to both the common name mure was applied. The dye-stuff was procured by puncturing a vessel in the throat of the larger genus, and by pounding the smaller entire. The tints capable of being imparted by this material were various—representing numerous shades between purple and crimson, but the imperial tint was that resembling coagulated blood. That it was known to the Egyptians, in the time of Moses, is sufficiently obvious from the testimony of more than one Scriptural passage. Ultimately, in later ages, a restrictive policy of the eastern emperors caused the art to be practised by only a few individuals, and at last, about the commencement of the twelfth century, when Byzantium was suffering from attacks without and dissensions within, the secret of imparting the purple dye of Tyre was lost.