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cracked grit, until it arrives at an impermeable freestone, 
which forms a barrier to further descent ; and having coursed 
with the dip, along its bearing level for some distance, the 
subterranean stream is relieved by various springs, one of 
which issues at the point stated, with an average volume of 
about 50 gallons per minute. 
During the long- continued drought of last summer, some 
scarcity was experienced, but these springs have a constant 
discharge, though variable in quantity, as also in tempera- 
ture, with the seasons. 
Silica is not found in large quantity in these springs, but 
in the absence of much lime it may be considered sufficient to 
characterize the water. It is a substance very sparingly 
soluble in cold water, though more abundantly so in hot, as 
is displayed in certain thermal springs, especially those in 
the island of St. Michael's, where the most perfect and 
genuine petrifactions are obtained by the deposit of silicious 
sinter, as it is called. Herbage, branches of ferns, and reeds, 
more or less miner ally encrusted with silex, are found ex- 
hibiting the successive steps from the soft state to a more 
complete conversion into stone. 
In a medicinal point of view, the Horley Green spring is 
perhaps the most important in the parish, its predominant 
ingredient affording us a striking example of the presence of 
iron. 
This metal, so profusely scattered in nature, met with in 
almost every mineral formation, and disseminated in every soil, 
is in minute quantity held in solution by nearly every spring, 
and so copious is its impregnation in many instances, as to 
stain the rocks and herbage as it passes, and to bind together 
sand, clay, and gravel into solid masses. From an analogous 
process to that now going on, it may be reasonably inferred, 
that the sandstones and other rocks in the sedimentary strata 
of ancient lakes, estuaries, and seas, have very probably been 
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