Page:The American Cyclopædia (1879) Volume VIII.djvu/252

 238 GREENSAND of science. Remains of several crustaceous ani- mals, as crabs, are also met with, and finely preserved specimens of various species of the echinodermata, and of zoophytes, sponges, &c. The shells which most abound in the greensand, occasionally making up the principal portion of the layers in which they occur, are gryphseas, terebratulas, ostreas, belemnites, and the ex- ogyra costata, the last named a very common and large bivalve peculiar to the cretaceous group. The greensand is of importance for its fertilizing property; and this is found to be derived, not from the calcareous nature of its organic remains, but from the green grains which commonly make up the greater portion of its beds. These, as they are found in New Jersey, when separated from adhering sand and clay, present a composition varying only within a limited range, and not differing from that of the greensand near Havre, France, as determined by Berthier. But according to the analysis of Dr. Turner, the same mineral sub- stance of Kent, England, is deficient in the very element, potash, to which its valuable qualities in this country are essentially owing. Some of the same material also met with in Marsh- field, Duxbury, and Gay Head, Mass., resem- bles the English in this particular. The mean of four analyses of New Jersey greensand, made by John C. Smock and E. H. Bogardus in 1865- '8, and the result of the examination of foreign specimens, are given in the following table : CONSTITUENTS. N. J. France. Gay Heid. England. Silica... Potash 48-50 9'00 50-00 10-90 56-70 48-50 Lime. 1'50 i'62 Alumina 8-00 7 : 66 13-82 17-00 Protoxide of iron Peroxide of iron Water. . . 5-00 1 21-00) 9*00 21-00 11-00 20-10 T'OO 22-00 7*00 Magnesia 1*18 8*80 In New Jersey the greensand (there called marl) is dug from pits during the winter, and brought out upon the fields, where it is spread to be ploughed in. The effect is experienced with the first crop, and continues for several years. The investigations of Ehrenberg first showed that many of the greensand grains are casts of the microscopic shells of polytlialamia (the many-chambered) and of other organic bodies. The shells themselves had disappear- ed ; but the internal form of their cavities was retained in the more durable silicate of iron, which took the place of the animal bodies as these decayed, and preserved their shapes. Even the very finest canals of the cell walls, and all their connecting tubes, are thus pet- rified and separately exhibited. Many of the grains which cannot be recognized as of this origin still suggest some connection with ani- mal bodies by their forms being sometimes lobed and again presenting the appearance of coprolites. Prof. Bailey by his experiments confirmed the conclusions of Ehrenberg, and, extending his investigations to cretaceous rocks GREEN UP from Alabama and W. Texas, found attached to them grains of greensand exhibiting the same phenomena. From specimens of marl and limestone of the eocene of the southern states he also succeeded in bringing to light similar grains of the same character by dissolv- ing away with dilute acid the calcareous mat- ters. One of his specimens was brought up in sinking the artesian well at Charleston from the depth of 140 ft. The soundings of the coast survey brought up from the depths of the ocean, in the Gulf stream and the gulf of Mex- ico, something resembling greensand. Count Pourtales reports one sounding as of this char- acter obtained in lat. 31 32', Ion. 79 35', at the depth of 150 fathoms. This, as well as the others referred to, were examined by Prof. Bai- ley, who found them to be greensand, and that this is often in the form of well defined casts of polythalamia, minute mollusks, and branch- ing tubuli. The material he found to be the same as that of the fossil casts ; but the chief part of the soundings he found consisted of perfectly preserved shells of the same species, which retained their brilliant colors, and gave evidence by treatment with acid that the soft parts were still present, thus proving the re- cent existence of the animals. Hence it ap- pears that in some deep seas the production of greensand is still going on, and formations of this obscure material are there growing up by the same agencies which elaborated those of ancient geological periods. GREENSBORO, a town and the capital of Hale co., Alabama, 80 m. W. by N. of Montgomery ; pop. in 1870, 1,760, of whom 972 were col- ored. It is surrounded by large cotton plan- tations, has a flourishing trade, and contains a court house, a jail, two banks, and several churches, and has a weekly newspaper. It is the seat of the Southern university (Methodist), which in 1872 had 13 professors and instructors, 120 students, and a library of 10,000 volumes. GREEN SNAKE. See COLUBER. GREENSTONE, a trappean rock of granular texture, either crystalline or compact, composed of hornblende and orthoclase, or augite with either orthoclase or albite. When albite re- places orthoclase, the rock is called diorite. Its greenish color is due to minute quantities of chromium compounds. It is called trap when in columnar form. Basalt is essentially the same rock. Being of irregular fracture, too hard to cut, and lacking uniform grain, it is unfit for use in building except of rough walls. (See BASALT, and TRAP.) GREENUP, a N. E. county of Kentucky, bor- dering on the Ohio river ; area 480 sq. m. ; pop. in 1870, 11,463, of whom 461 were col- ored. It is hilly and well timbered, has a fer- tile soil, and abounds in coal and iron. The chief productions in 1870 were 29,842 bushels of wheat, 164,650 of Indian corn, 26,864 of oats, 9,498 of potatoes, and 1,668 tons of hay. There were 747 horses, 533 milch cows, 1,624 other cattle, 2,086 sheep, and 2,834 swine; 7