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The calcareous strata of the Scotch coal-fields, those of Lanarkshire, the Lothians, and Fife, for example, are very insignificant in thickness when compared to those of England. They consist of a few beds intercalated between the sandstones and shales containing coal and ironstone, the combined thickness of all the limestones amounting to no more than 150 feet.
In a slab of sandstone, not more than an inch thick, the furrows or ridges of an ancient ripple may often be seen in several successive laminae to run towards different points of the compass. Successive Deposition indicated by Fossils. Limestones formed of Corals and Shells. Proofs of gradual Increase of Strata derived from Fossils. Serpula attached to Spatangus. Wood bored by Teredina.
At Predazzo, in the Tyrol, secondary strata, some of which are limestones of the Oolitic period, have been traversed and altered by Plutonic rocks, one portion of which is an augitic porphyry, which passes insensibly into granite. The limestone is changed into granular marble, with a band of serpentine at the junction.
Werner had found the granites, limestones, sandstones, schists, etc., occurring in a certain relative order in his native country; and he drew the very remarkable conclusion that this was the normal order in which these various rocks would invariably be found in all parts of the world, on the theory that this was the order in which these different rocks had been formed in the beginning, great layers of these different rocks having originally been spread completely around the globe one outside another like the coats of an onion.
Among the fresh-water strata of this age near the base of the Pyrenees are marls, limestones and sands, in which the eminent comparative anatomist, M. Lartet, has obtained a great number of fossil mammalia common to the faluns of the Loire and the Upper Miocene beds of Switzerland, such as Dinotherium giganteum and Mastodon angustidens; also the bones of quadrumana, or of the ape and monkey tribe, which were discovered in 1837, the first of that order of quadrupeds detected in Europe.
The remains of reefs formed by coral polypes of different kinds from those which exist now, enter largely into the composition of the limestones of the Jurassic period; and still more widely different coral polypes have contributed their quota to the vast thickness of the carboniferous and Devonian strata.
Limestones are formed in the same manner from the grinding up of other sea-shells and fossils, various in kind; the powder becoming gradually united into solid rock. There is yet another way in which limestone is made, quite different from all these. Sometimes streams of water have a large quantity of lime in them; and these as they flow will drop layers of lime which harden into rock.
Long enough ago, in Trinidad at least, to allow water probably the estuary waters of the Orinoco to saw all the upheaved layers off at the top into one flat sea-bottom once more, leaving as projections certain harder knots of rock, such as the limestones of Mount Tamana; and, it may be, the curious knoll of hard clay rock under which nestles the town of San Fernando.
You may see in the galleries of the Museum up stairs specimens of limestones in which such fossil remains of existing animals are imbedded. There are some specimens in which turtles' eggs have been imbedded in calcareous sand, and before the sun had hatched the young turtles, they became covered over with calcareous mud, and thus have been preserved and fossilized.
While the two governments were exchanging diplomatic notes, fifteen patents were taken out in England for the extraction of sulphuric acid from the limestones, iron pyrites, and other mineral substances in which England abounds.
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