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 might almost say magic element with which it is pervaded.

In attempting to classify the compositions in Frézier's book one is staggered by the grotesque character of many of them and by the extraordinary variations in the proportion of their ingredients, even amongst compositions designed for a similar effect.

Presumably with the intention of impressing his readers with the wonders of the science, he added ingredient after ingredient, which, if they did actually no harm to the composition, certainly in no degree assisted its functioning.

In what he calls a simple star there are eleven ingredients, of which, in fact, four only are essential.

Further, beyond the multiplication of unnecessary ingredients in individual compositions, there is often their incompatibility and innate unsuitability for the purpose. Such components as ink, onion juice, and the drainings of a dung-heap suggest so strangely the formulæ of the alchemists that one almost expects to come across "the hair of a Barbary ape," or similar absurdity.

Ruggieri, who may be considered as the last of the old school, is the first author to deal with the subject in such a way as to convince the professional reader of the practical knowledge of the subject.

His additions to the list of ingredients are not many, but they are genuine. He is the first writer to make use of metals or their salts in the production of colour; he includes among his chemicals metallic copper and zinc, also the acetate and sulphate of copper, and chloride of ammonium. The notable advance in his colour compositions, besides the use of metal salts for that purpose, is the introduction of a chloride, which has the effect of improving the colour by assisting in the volatilisation of the metal. For this purpose he used sal-ammoniac, the use of which has now been almost discontinued on account of its hygroscopic nature, notwithstanding that its