10 PHILOSOPHICAL TRANSACTIONS. [aNNO 1770. 



by means of a tin cylinder, containing a large quart, with an apparatus so con- 

 trived, as to keep the thermometer standing upright in the middle, without 

 touching its sides: thus inclosed in a case, filled with water from along side, and 

 covered with a cap,, so as to be perfectly water tight, he sunk, it with the deep- 

 sea sounding lead ; letting it hang just clear of the ground for the space of half an 

 hour, and then had it hauled up as briskly as possible, and the case being in- 

 stantly opened, he inspected the thermometer. He found the inconvenience 

 however of making the experiment in this way, because of the length of time 

 necessary; therefore he made a very small hole in each end of the cylinder, to let 

 the water in and the air out, and sent it down empty, that it might fill as far 

 below the surface as possible, suffering it however always to hang a few minutes, 

 that it might be full before he caused the boat's crew to begin hauling it up. The 

 lead, with this apparatus fastened to the line a little above it, sunk 26o fathoms 

 in 3-1- minutes, and was hauled up in J 3^. 



VIL On the Manner in which White Marble is produced. By R. S, Raspe, 

 F.R.S. An Abstract from the Latin, p. 47. 



In this paper Mr. R. gives an account of some observations made by the Abbe 

 Vegni on the hot mineral waters of St. Philip, situated at Radicofani, in Tuscany, 

 on the road from Florence to Rome. 1° The Abbe traced the source of these 

 waters to a small hill (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 shin- 

 ing 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 further observed, that when the old chan- 

 nels 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 Abbe 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. 2° That this tophaceous precipitate might be rendered 

 subservient to the arts, provided it was caught upon moulds. Accordingly the 

 Abbe set on foot an undertaking of this kind, which succeeded very well. Mo - 

 dels 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 in the space of 6 days ; 

 and in this manner were obtained has reliefs, medallions, architectural ornaments 



