We do not mean to dwell upon this ingenious speculation, which would carry us too far from the object at which we are aiming. It seems to us, however, that the arguments in its favor are at least deserving of careful consideration; and we may add that they receive new strength from the facts we shall have occasion hereafter to bring forward, when we come to speak of the undulating movements to which the Crust of the Earth has been subject at many different times, and in many different localities, even within the historic period. The formation and structure of existing Coral Reefs being once fairly established, Geologists have little difficulty in ascribing a similar origin to many of the limestone strata that are found in the Crust of the Earth. For though the internal texture has been considerably modified in the long course of ages, by chemical and other influences, nevertheless the stony skeletons of the reef-building Zoophytes can be distinctly recognized in great abundance. Indeed it is not an uncommon thing to meet with limestone rock exhibiting plainly to the eye all the appearance of Coral Reefs lifted up from the bed of the ocean. “The Oolite,” says Doctor Mantell, “abounds in corals, and contains beds of limestone which are merely coral reefs that have undergone no change but that of elevation from the bottom of the deep, and the consolidation of their materials. The Coral-rag of Wilts presents in fact all the characters of modern reefs: the polypifera belong chiefly to the Astræidæ, the genera of which family principally contribute to the formations now going on in the Pacific. Shells, echinoderms, teeth, and bones of fishes, and other marine exuviæ, occupy the interstices between the corals, and the whole is consolidated by sand and gravel, held together in some instances by calcareous, in others by siliceous infiltrations. Those who have visited districts where the Coral-rag forms the immediate subsoil, and is exposed to view in the quarries or in natural sections, must have been struck with the resemblance of these rocks to modern coral banks.”[56] Even in many of our finest marbles the coral skeletons may be traced distinctly enough, and contribute not a little to that variegated color which is so much admired. Nay, it is recorded by Mr. Parkinson that he discovered in a piece of solid marble, the _animal membrane itself_ by which the lime was originally abstracted from the sea. He immersed the marble in dilute muriatic acid; and he relates with delight how, as the calcareous earth dissolved, and the carbonic acid gas escaped, he observed the animal tissue begin distinctly to appear in the form of light, elastic membranes.[57] [Illustration] [Illustration] CHAPTER IX. STRATIFIED ROCKS OF ORGANIC ORIGIN--ILLUSTRATIONS FROM VEGETABLE LIFE.