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For carbonate of lime is a widely-spread substance, and is met with under very various conditions. All sorts of limestones are composed of more or less pure carbonate of lime. The crust which is often deposited by waters which have drained through limestone rocks, in the form of what are called stalagmites and stalactites, is carbonate of lime.
In these two regions limestones, sandstones, and clays of the Secondary and Tertiary formations alone crop out at the surface, so that the travelled fragments of Alpine origin can easily be distinguished and in some cases the precise localities pointed out from whence they must have come. Maclaren will enable the reader more fully to appreciate the line of argument relied on by M. Guyot.
Such fossils, therefore, are almost confined to the limestones; but an exception occurs at Bradford, near Bath, where they are enveloped in clay sometimes 60 feet thick.
The Ozark region was thus the first land to appear within the borders of the present state of Missouri." He further says: "Although it has long been known that the Magnesian Limestones are older than the Trenton, and that they lie immediately upon and against the Archæan crystallines unconformably, their exact geological age has always remained unsettled.
The limestones of the early and middle Ordovician show that now the shore had become remote and the lands had become more low. The waters now had cleared. Colonies of brachiopods and other lime-secreting animals occupied the sea bottom, and their debris mantled it with sheets of limy ooze.
If we examine with the microscope the fine-grained silts which make up the shaly layers between limestones, we find the materials to be mostly of inorganic origin.
For this reason, as well as because I have not found here the near studies of primitive rock I expected, for to my great surprise, I find the whole group of mountains, mighty as they are, except the inaccessible Monte Rosa, of secondary limestones or slates, I should like, if it were possible, to spend a couple of days more on the Montanvert, and at the bases of the Chamouni aiguilles, sleeping at the Montanvert."
In the latter case its presence seems to prove still more clearly that the limestones of Cumanacoa and Caripe are only two parts of the same system, alternating with sandstone, sometimes quartzose, sometimes slaty.
In certain parts of the Morea, the age of these volcanic rocks is established by the following proofs: first, the lithographic limestones of the Cretaceous era are cut through by trap, and then a conglomerate occurs, at Nauplia and other places, containing in its calcareous cement many well-known fossils of the chalk and greensand, together with pebbles formed of rolled pieces of the same serpentinous trap, which appear in the dikes above alluded to.
Some of this same tribe of shells, such as Camarophoria, allied to Rhynchonella, Spiriferina, and two species of Lingula, are specifically the same as fossils of the carboniferous rocks. Restored outline of a fish of the genus Palaeoniscus, Agassiz. Beneath the limestone lies a formation termed the marl-stone, which consists of hard calcareous shales, marl-slate, and thin-bedded limestones.
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