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ginal appearance. All these colours I have introducedinto glass by preparations of gold ; and I have found themto be nearly as perishable in the fire when the colouredgold powder was thus diffused through the glass, as whenexposed to the fire by itself: when the fire was raised toany great degree, and the glass made to flow thin, therewas generally a button of revived gold collected at thebottom.

A solution os' gold in aqua regia being inspissated todryness in the bottom of a Florence flask, ancf the heatfurther increased till the gold resumed its proper colour,the lower part of the glass was by this simple processtinged purplish : pieces of it being exposed to the flameof a lamp, they became in some parts violet coloured, insome of a bright purple, and in others purplish red ; and.the parts which in one position looked violet or purplish,,in another appeared red.

A colour nearly of the same kind is impressed on glassby gold leaf in some electrical experiments ; a fact which,we are obliged to Mr. Franklin for the first knowledge of.A narrow strip of gold leaf being placed between two flipsof glass, with both the ends hanging out a little, and theglass well.tied round with silk thread, a strong electricalexplosion is made to pass through the gold leaf. On ex-amining the glass, the gold leaf, he observes, will be foundmisting in several places, and instead of it a reddish stainon both the glasses, exactly similar on both in the minuteststroke, though sometimes spread a little wider than thebreadth of the leaf: the stain appears to have penetratedinto the substance os the glass, so as to be protected by itfrom the action of aqua regia. I have had this experimentseveral times repeated with plate glass, and found it tinged,,as above described, in some parts violet, in some purplish,.and in some reddish ; the colours could not be scraped ostj

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