. The elements of geology, for popular use : containing a description of the geological formations and mineral resources of the United States. Geology; Geology. 106 UPPER SECONDARY ROCKS. Fig-. A, Portland Marine Limestone; B, Ancient Forest in the Dirt- Bed ; C, Lower Purbeck Beds of fresh-water Limestone. The upper series of the secondary formations con- sists of beds of green sand and chalk. In England, France, and Germany, this comprises a formation of great depth, computed to be at least one thou- sand feet in thickness, and its exclusively marine fossils prove that it was formed ben
. The elements of geology, for popular use : containing a description of the geological formations and mineral resources of the United States. Geology; Geology. 106 UPPER SECONDARY ROCKS. Fig-. A, Portland Marine Limestone; B, Ancient Forest in the Dirt- Bed ; C, Lower Purbeck Beds of fresh-water Limestone. The upper series of the secondary formations con- sists of beds of green sand and chalk. In England, France, and Germany, this comprises a formation of great depth, computed to be at least one thou- sand feet in thickness, and its exclusively marine fossils prove that it was formed beneath the ocean. The lower part of this group has been usually called the green sand formation, because it abounds in green-coloured grains, which give, on analysis, silex, protoxide of iron,* alumine, and potash. This is separated from the chalk above by a bed of gray- ish blue clay, called gault, effervescing strongly, and containing some fossils. The green sandf is thus divided into the upper green sand, the gault, and the lower green sand. The lower green sand is very fer- ruginous, containing beds of sand more indurated towards the bottom with limestone in some locali- ties. The upper green sand is a mass of stratified sands, containing a large portion of the green grains, and * M. Berthier has analyzed the green particles, and found in every 100 parts 50 of silica, 21 of iron, and the remainder to consist of alumine, potash, and water. t Prof. Ren wick states that green sand owes its colour to a chloritous silicate of 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; Draper, Daniel, 1841-1931, donor. DSI. New-York : Harper & Brothers
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Keywords: ., bookcentury1800, bookpublishernewyorkharperb, booksubjectgeology
