180 



CALCAREOUS SPRINGS. 



into several pits, in which it deposites carbonate 

 and crystals of sulphate of lime. After being thus 

 ^ freed from its grosser parts, it is conveyed by a tube 

 to the summit of a small chamber, and made to 

 fall through a small space of 10 or 12 feet. The 

 current is broken in its descent by numerous cross- 

 ed sticks, by which the spray is dispersed around 

 upon certain moulds, which are rubbed hghtly over 

 with a solution of soap, and a deposition of solid 

 matter like marble is the result, yielding a beautiful 

 cast of the figures formed in the mould. A hard 

 stratum of stone about a foot thick is obtained from 

 the waters of these springs in four months. They 

 have formed a deposite of limestone a mile and a 

 quarter in length, a third of a mile in breadth, and 

 in some places -250 feet thick. What renders this 

 limestone of peculiar interest to the geologist, is 

 the spheroidal or globular form which it assumes. 

 Some of the concentric masses are cojnposed of lam- 

 inae so thin that 60 may be counted in the thick- 

 ness of an inch. This tendency to a globular struc- 

 ture doubtless arises from the facility with which 

 the calcareous matter is precipitated in nearly equal 

 quantities on all sides of any fragment of shell or 

 wood, or any inequality of the surface over which 

 the mineral water flows. Such concretions often 

 form on the internal surface of steam boilers, the 

 head of a nail or rivet forming the nucleus, which 

 becomes covered by a series of overlapping crusts 

 of calcareous matter, usually sulphate of lime. 



Near Viterbeo, in Italy, there is a hill about 20 

 feet high and 500 yards in circumference entirely 

 composed of limestone deposited from water. This 

 has been quarried for building-stone, and the strata 

 have concentric and radiated structure. A spring 

 near Civita Vecchia, in Italy, deposites alternate 

 beds of a yellowish travertin and a white granular 

 rock, not distinguishable either in grain, colour, or 

 composition from statuary marble. 



