180 
CALCAREOUS SPRINGS. 
into several pits, in which it depositee 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, vv^hich are rubbed lightly 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 composed of lam- 
inae so thin that 60 may be counted in the thicks 
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 crust? 
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. Thii^ 
has been quarried for building-stone, and the strata 
have a concentric and radiated structure. A spring 
near Civita Yecehia, 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. 
