Limestone
3 of the 7 encyclopedias on this shelf carry an entry for Limestone. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a well known and widely distributed rock. It consists chiefly of carbonate of lime. Magnesium, iron oxide, alumina, and silica are usually present. Most limestones are formed in comparatively shallow, clear seas by the accumulation of shells. Some of these shells are so small that they require a microscope to make them out. Coral and shells of mollusks contribute largely. Sometimes limy materials are ground to a fine ooze before they consolidate. Sometimes they remain almost entire. A close examination of a limestone will reveal usually a large number of fossils, ranging in size from the head of a pin to shells several feet in length or diameter. Some of the later limestones are a mere mass of shells. The varieties of limestone are endless. Some are pure white, others yellow, others are blue, and others again, when stained with bitumen, are black. Under great heat and pressure limestone is converted frequently into marble of various colors, sometimes beautifully mottled. Chalk is a soft, powdery limestone. Some limestones are so full of sand that it is difficult to distinguish them from sandstones. At the other end of the series, they pass into marls and shales. Disintegrating limestone makes rich soil. The famous blue grass region of Kentucky and other sections owe their reputation to an underlying layer of limestone that disintegrates just fast enough to feed the soil. Crops grown on a limestone soil withstand early frosts and drought well. Our limestone quarries lead those of all other countries in money value. For some of the purposes to which limestone is put, see MARBLE; LIME; CEMENT.
Collier's New Encyclopedia (1921)
a general name for all rocks the basis of which is carbonate of lime. It is not generally pure, but has in it alumina, silica, etc. In regions such as Auvergne and Tuscany, in which extinct volcanoes exist, hundreds of springs, both cold and thermal, rise to the surface, bringing up from the subeeding terranean depths carbonate of lime. The men for 1 quantity thus transferred to the surface Eor food. in the course of ages is enormous, and the sea an manifold streams and rivers carry it into Leher (H the sea. Mollusks withdraw it for their ingly dext shells, corals for their reefs, and in due asks from time the upheaval of the sea bed conimals from verts it into a terrestrial limestone rock. N, a city Metamorphic action can destroy it, and tself; capi there is little limestone in rocks which . of Londd have undergone such a change. When junction of what used to be called primitive, now identified crystalline or metamorphic, limestone is lonia, arte found in such beds, it is probably of organic Conquerd origin. Modern limestones are strength often composed entirely of organic remains or are studded thickly with them. the 11th Thus crinoidal or encrinital limestone is composed chiefly of encrinites, chalk of hin whic foraminifers, nummulitic limestone of "Great nummulites, and shells of Saccamina, or eracked in of spindle-shaped Fusulina. Sometimes new bell. limestone may be brecciated, concretion- -uildings ary, compact, magnesian, etc. of the
The Encyclopedia of Founding (1892)
The name given to all rocks which are composed to a great extent of carbonate of lime. The chief varieties of limestone are chalk; oolite, compact limestone of the hard, smooth, fine-grained rock, of a bluish-gray color; crystalline limestone; and statuary marble. Magnesian limestone or dolomite is a rock in which carbonate of magnesia is mixed with carbonate of lime. See DOLOMITE.