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tastic forms, tapering spire and minaret, huge towers, bastions, and 
buttresses of rock that imitated as it were the ideas of the medizval 
architect. It was the same more or less in all hilly limestone districts. 
Chemistry afforded us the clue to this. Ona small scale he could 
imitate Nature with this bottle and test tubes. The rain falling through 
the atmosphere absorbed the carbonic acid gas which was always present 
there. The water, thus become acid by the presence of this gas in it, 
exerted a much greater solvent power onthe rocks. Their softer parts 
yielded to it the more easily, the harder ones remained, constituting 
the varied forms of which he had spoken. The experiment would also 
illustrate the deposition of lime by the dropping wells which were 
among the curiosities of Matlock. As the carbonic acid evaporated, 
the stony matter which the water held in solution by virtue of the 
presence of the gas in it was precipitated. Thus the tufa was formed 
also, which constituted large beds in the neighbourhood of these 
streams of acidified water. Of such masses of water-deposited rock 
Rome itself was built. But the action of carbonic acid was one of the 
most potent forces at work in disintegrating the surface of the land. 
Filter, for instance, the mud from the waters of the Thames, and the 
limpid clear liquid that remained still held in solution a large quantity 
of matter dissolved in it. In this way that river carried down to the 
sea, according to Ramsay, 300,000 ‘tons of carbonate of lime every 
year. Thirty million tons were thus dissolved out of the valley of the 
Thames every century by the chemical action of the stream. 
A section of the High Tor at Matlock afforded a good example of 
the character of the mountain limestone in the neighbourhood. That 
the mountain limestone was of marine origin all were aware. The 
presence of corals, spirifers, terebratula, were abundant proof of this. 
But there were some peculiarities which were interesting. He had 
imagined that chert flints, for instance, were peculiar to the chalk. But, 
~ on the summit of the High Tor, was the familar face of the black 
flint nodules and the white chert. The silicious matter existed 
in the ocean beds of those primeval times as in the latter ones of 
our chalk. Before them on the table were some specimens of 
what the miners termed toad-stone. Its murky dismal colours, 
interspersed with spots, had doubtless acquired for it such a 
name, and yet it was the most interesting of this series of rocks. 
The curved lines of the strata in the High Tor told their tale of the 
enormous forces which upheaved and bent nearly double these vast 
