VII. On the Manner in which White Marble is produced. By R. S. Raspe, F.R.S. An Abstract from the Latin, p. 47. (1770)

The Philosophical Transactions of the Royal Society of London, For their commencement, in 1665, to the year 1800: Abridged, with notes and biographic illustrations by Charles Hutton, LL.D. F.R.S. George Shaw, M.D. F.R.S. F.L.S. Richard Pearson, M.D. F.S.A. VOL XIII From 1770 to 1776. London: Printed by and for C. And R. Baldwin, New Bridge-Street, Blackfriars. 1809In this paper "Mr. R. gives an account of some observations made by the Abbé Vegni on the hot mineral waters of St. Philip, situated at Radicofani, in Tuscany, on the road from Florence to Rome. 1° The Abbé traced the source of «hese waters to a small bill (which appeared to be entirely composed of white marble), from which they flowed in several rivulets. 2° He found that these waters abounded in sulphur. 3° He found that they deposited a great quantity of shining white tophus, with which not only the sides of the channels, along which they flowed, became incrusted, but likewise all kinds of hard bodies that were thrown into them; and this in such manner, that when the said tophus was dexterously broken off, it retained exactly the form and shape of the bodies on which it had been deposited. 4° He furtlier observed, that when the old channels became choked up by - the accumulation of tophus, or in any other manner, the water still continued to deposit tophus in its new and more elevated channels.

Hence the Abbé was led to infer, 1° That the whole of that hill, from which these hot mineral waters issued, was formed by the successive deposition of this shining white tophus. 1° That this tophaceous precipitate might be rendered subservient to the arts, provided it was caught upon moulds. Accordingly the Abbé set on foot an undertaking of this kind, which succeeded very well. Models of various kinds of sculpture formed of gypsum, well varnished and be smeared with oil or grease, being placed in the currents of these hot springs, became incrusted with tophus to the thickness of 1 lines -m the space of 6 days; and in this manner were obtained bas reliefs, medallions, architectural ornaments for doors, windows, chimneys, &c. which in many instances looked like real sculpture, and seemed to be formed of the purest Carrara marble.

Mr. Raspe adopts the opinion that all white marble is a precipitate from water like the tophus of the hot springs above mentioned.

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