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The gneiss close to the fragments generally contained many large crystals of hornblende, which are entirely absent or rare in other parts: its folia or laminae were gently bent round the fragments, in the same manner as they sometimes are round concretions.
It consisted of a very hard conglomerate composed of irregular concretions of milk-white quartz, in a ferruginous basis, with apparently compact felspar weathering white.
The spirit hovering above the spires was as different from its concretions in their caps and gowns as ever the spirit of Christ was from church dogmas. "Shall we go into Grinnings'?" asked Shelton, as they passed the club. But each looked at his clothes, for two elegant young men in flannel suits were coming out. "You go," said Crocker, with a smirk. Shelton shook his head.
Aymestry. One-half natural size. a. View of both valves united. b. The chief mass of this formation consists of a dark grey argillaceous shale with calcareous concretions, having a maximum thickness of 1000 feet. In some places, and especially at Aymestry, in Herefordshire, a subcrystalline and argillaceous limestone, sometimes 50 feet thick, overlies the shale.
It attains a thickness of about 100 feet, and though very different in age, much resembles in mineral character the "London clay," containing, like it, septaria or concretions of argillaceous limestone traversed by cracks in the interior, which are filled with calc-spar. The shells, referable to about forty species, have been described by MM. Nyst and De Koninck.
There are just two distinct views under which we may consider all stalactical concretions formed; these are the incrustation of the calcareous substance concreting upon a foreign body, and the incrustation of the same substance upon itself. By the first any manner of shape may be formed, provided there be a solid body, upon the surface of which the calcareous solution is made to pass.
The surrounding ashes do not contain any carbonate of lime; hence the concretions have probably been formed, as is so often the case, by the aggregation of this substance. I have not met with any account of similar concretions; and considering their great toughness and compactness, their occurrence in a bed, which probably has been subjected only to atmospheric moisture, is remarkable.
Nothing is more common than this appearance. Cavities are every where found closely lined with crystallizations, of every different substance which may be supposed in those places. These concretions are well known to naturalists, and form part of the beautiful specimens which are preserved in the cabinets of collectors, and which the German mineralists have termed Drusen.
Were the crystallization and configuration found to proceed from a central body, and to be directed from that centre outwards, then, without inquiring into collateral appearances, and other proofs with regard to the natural concretion of those substances, we might suppose that these concretions might have proceeded from that central body gradually by accretion, and that the concreting and crystallizing substances might have been supplied from a fluid which had before retained the concreting substance in solution; in like manner as the crystallizations of sugar, which are formed in the solution of that saccharine substance, and are termed candies, are formed upon the threads which are extended in the crystallizing vessel for that purpose.
After things are discovered, however, they may be used as terms in a second ideal synthesis and a concretion in discourse on a higher plane may be composed out of sustained concretions in existence. Proper names are such secondary concretions in discourse.
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