PETRIFYING SPRINGS. 
In volcanic regions, or in those where earthquakes have occurred at a 
comparatively recent date, springs are frequently loaded with mineral 
substances, which they abundantly deposit in their course. In many 
parts of Italy, the accumulation of chalky matter deposited by springs is 
so great, as to form rocks of much solidity and strength. The water 
which supplies the baths of San Filippo in Tuscany contains lime and 
magnesia, and has been known to deposit a solid mass thirty feet thick, 
in the course of twenty years. Extensive layers of this stony substance 
are found in the neighbourhood of the springs,, reaching a mile and a 
quarter in length, the third of a mile in breadth, and in some places 
attaining a thickness of two hundred and fifty feet. 
The more loose and porous rock resulting from such springs, generally 
contains incrusted plants and other substances, and is called tufa ; the 
more compact is called travertin; and is quarried for building pur- 
poses. Many of the most splendid edifices in Rome are built of this 
stone. 
The whole western part of Asia Minor is full of petrifying springs, and 
even the rivers are loaded with mineral substances. Where the ancient 
city of Hierapolis once stood, there is a remarkable mass of rock, formed 
by the tufa, or soft stone, which the springs deposit, This rock appears 
like an immense frozen cascade, and is, in fact, the petrifaction of falling- 
waters. Dr. Chandler thus describes this Petrified Cascade : — The view 
before us was so marvellous, that the description of it, to bear even a 
faint resemblance, ought to appear romantic. The vast slope which at a 
distance we had taken for chalk, was now beheld with wonder, it seeming 
an immense frozen cascade, the surface wavy, as of water at once fixed, 
or in its headlong course suddenly petrified. Round about us were many 
high, bare, stony ridges ; and close by our tent one with a wide basis, and 
a slender rill of water, clear, soft, and warm, running in a small channel 
on the top." The whole region abounds with marks of volcanic action, 
and the waters have long been celebrated for their extraordinary petrify- 
ing powers. It is related that in order to make stone fences round the 
gardens and vineyards of Hierapolis, it was only necessary to conduct the 
water into narrow channels, and they soon became filled up with stone. 
Dr. Chandler found numerous ridges or fences thus formed, and even a 
road which appeared a wide and high causeway, proved to be a petri- 
faction. 
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