. The elements of geology, for popular use : containing a description of the geological formations and mineral resources of the United States. Geology; Geology. 124 BASALTIC DIKES. low or deep red colour, and the chalk is highly phosphorescent. Fig. Ill, Chalk changed into marble. 2 2, Trap dikes. In Anglina, a dike 134 feet wide, consisting of a rock composed of feldspar and augite, penetrates strata of shale and argillaceous limestone, which it cuts perpendicularly ; these are found changed to a distance of thirty-five feet from the edge of the dike. The shale, as it approaches the trap
. The elements of geology, for popular use : containing a description of the geological formations and mineral resources of the United States. Geology; Geology. 124 BASALTIC DIKES. low or deep red colour, and the chalk is highly phosphorescent. Fig. Ill, Chalk changed into marble. 2 2, Trap dikes. In Anglina, a dike 134 feet wide, consisting of a rock composed of feldspar and augite, penetrates strata of shale and argillaceous limestone, which it cuts perpendicularly ; these are found changed to a distance of thirty-five feet from the edge of the dike. The shale, as it approaches the trap, be- comes gradually more compact, and is most indu- rated where nearest the junction. Here it becomes a hard porcellaneous jasper. The limestone also loses its earthy texture as it approaches the dike, and becomes granular and crystalline. The altered shale also contains crystals of garnet and analcime, while they are found in no other 'portion of the rock. In the county of Antrim, also, chalk with flints is traversed by basaltic dikes, and changed, for a distance of ten feet from the dike, into granular marble. In the same manner, red sandstone has been con- verted into hornstone,* and soft slate clay changed into flinty In Ireland, one of the greenstone dikes of Antrim, on passing through a bed of coal, reduces it to a cinder for the space of nine feet on each side. The same fact has been noticed at Cockfield Fell, in the north of England. Here spe- cimens taken at a distance of thirty yards from the dike resemble common pit-coal; those nearer the * Geol. Transactions, first series, vol. iii., p. 201. t Ibid,, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lee, Charles A. (Charles Alfred), 1801-1872. New-York : Harper & Brothers
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectgeology, bookyear1846
