402 



TEAVERTIN OF SAN FILIPPO. 



[Ch. XVII. 



of about 



half a mile east of San Yignone. The beds take 

 the slope of the hill at about an angle of 6°, and the planes 

 of stratification are perfectly parallel. One stratum, com- 

 posed of many layers, is of a compact nature, and fifteen feet 

 thick ; it serves as an excellent building stone, and a mass of 

 fifteen feet in length was, in 1828, cut out for the new bridge 

 over the Orcia. Another branch of it (a, fig. 28) descends 

 to the west, for a length of 250 feet, varying in thickn 



ess 



sometimes 



some 



into a valley till their progress is suddenly arrested by a 



earn 



The abrupt termination of the mass of rock at the river, 

 where its thickness is undiminished, clearly shows that it 

 would proceed much farther 



im 



if not arrested by the stream, 

 But it cannot encroach upon 

 the channel of the Orcia, being constantly undermined, so 

 that its solid fragments are seen strewed amongst the allu- 

 vial gravel. However enormous, therefore, the mass of solid 

 rock may appear which has been given out by this single 

 spring, we may feel assured that it is insignificant in volume 

 when compared to that which has been carried to the sea 

 since the time it began to flow. What may have been the 

 length of that period of time we have no data for conjectur- 

 ing. In quarrying the travertin, Roman tiles have been 

 sometimes found at the depth of five or six feet. 



Baths of San Filippo. — On another hill, not many miles 

 from that last mentioned, and also connected with Mount 

 Amiata, the summit of which is about three miles distant, 

 are the celebrated baths of San Filippo. The subjacent rocks 

 consist of alternations of black slate, limestone, and serpen- 



There are three warm springs containing carbonate 



The 



tine. 



and sulphate of lime, and sulphate of 



water which supplies the baths falls into a pond, where it has 



magnesia. 



been known to deposit a solid mass thirty feet thick in about 

 tiventy years.* A manufactory of medallions in basso-relievo 

 is carried on at these baths. The water is conducted by 

 canals into several pits, in which it deposits travertin and 



* Dr. Grosse on the Baths of San Filippo, Ed. Phil. Journ. vol. ii. p. 292. 











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