. The elements of geology, for popular use : containing a description of the geological formations and mineral resources of the United States. Geology; Geology. 62 FORMATIONS. if occupied by clay and soft materials, a clay dike. How these fissures came to be filled by sucii sub- stances will be a subject of inquiry hereafter. They vary in thickness from a few mches to hundreds of feet. When a series of strata of a similar rock are ar- ranged with occasional intervening strata of rocks of another kind, which recur in different parts of the series, they are regarded as having been all formed nea
. The elements of geology, for popular use : containing a description of the geological formations and mineral resources of the United States. Geology; Geology. 62 FORMATIONS. if occupied by clay and soft materials, a clay dike. How these fissures came to be filled by sucii sub- stances will be a subject of inquiry hereafter. They vary in thickness from a few mches to hundreds of feet. When a series of strata of a similar rock are ar- ranged with occasional intervening strata of rocks of another kind, which recur in different parts of the series, they are regarded as having been all formed nearly at the same epoch and under similar circumstances; and such beds are called by geolo- gists formations. Thus the strata of shale, sand- stone, and ironstone that accompany beds of coal, are called the coal formation. Strata of different kinds, in which a gradation is observed into each other, and which contain similar species of organic remains, also constitute a geological formation. The chalk with flints, the lower chalk without flints, the chalk marl, and the green sand under the chaik, are regarded as members of what is denominated the clialk formation.^^ There is one circumstance of frequent occurrence which is apt to confound the young geologist, and that is, in travelling in mount- ainous districts, after passing over a certain series i of rocks, he again meets with them in a contrary order. How this is accounted for figure 15 will help to explain. Fig. C c are parts of the lowest stratified rocks, a a oi the highest Now suppose them to be lying in a • 6ak»w«ll's Geology,. 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
