400 



CALCAREOUS SPRINGS. 



[Ch. XVII. 



encrusting 



spring m 



the 



me 



department, situated at 

 Chaluzet, near Pont Gibaud, rises in a gneiss country, at the 

 foot of a regular volcanic cone, at least twenty miles from 

 any calcareous rock. Some masses of tufaceous deposit, 

 produced by this spring, have an oolitic texture. 



>/ 



'om 



of Trance to that which skirts the Apennines in the Italian 



peninsula, we meet with innumei 



springs which have 



much calcareous matter 



m 



some parts of Tuscany is coated over with tufa and 



travertin, and sounds hollow beneath the foot. 

 In other places in the same 



com 



much 



seen descending the slanting sides of hills, very 



manner of lava currents, except that they are of a white 



terminate 



course 



of a river. These consist of a calcareous precipitate from 

 springs, some of which are still flowing, while others have 

 disappeared or changed their position. Such masses are 

 frequent on the slope of the hills which bound the valley of 

 the Elsa, one of the tributaries of the Arno, which flows near 

 Colle, through a valley several hundred feet deep, shaped 

 out of a lacustrine formation, containing fossil shells of 

 existing species. I observed here that the travertin was un- 

 conformable to the lacustrine beds, its inclination according 

 with the slope of the sides of the valley. One of the finest 

 examples which I saw was at the Molino delle Caldane, near 



Colle. 



small rivulets 



the Elsa, have the property of encrusting wood and herbs 

 with calcareous stone. In the bed of the Elsa itself, aquatic 

 plants, such as Charse, which absorb large quantities of car- 



lime 



Baths of San Vignone. — Those persons who have merely 

 seen the action of petrifying waters in England, will not 

 easily form an adequate conception of the scale on which the 

 same process is exhibited in those regions which lie nearer to 

 the active centres of volcanic disturbance. One of the nios 



exam 



lime 



in Tuscany, at a short distance from Radicofani, and only a 











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