Page:The American Cyclopædia (1879) Volume VI.djvu/198

 190 DOLOMITE Ponces, et Catalogue rauonne des produits de VEtna ; and on the nature of leucite, anthra- cite, pyroxene, &c. The Journal du dernier voyage du citoyen Dolomieu dans les Alpes was published by Bruun-Neergaard at Paris in 1802. DOLOMITE, a mineral species named in honor of the French geologist Dolomieu. It occurs crystallized in rhombohedral forms, and also as a rock of granular and crystalline structure. The mineral species includes several varieties, as brown spar, pearl spar, &c. Its hardness is 3-5-4 ; specific gravity, 2'85-2'92. The weight of a cubic foot of the rock is consequently about 180 Ibs. Dolomite is a magnesian carbonate of lime, consisting of one equivalent of carbon- ate of magnesia and one of carbonate of lime, or, in 100 parts, 45 -65 of the former and 54'35 of the latter. It is usually white, but is also found of various colors. It is largely developed as a metamorphic rock in the calciferous epoch of the Potsdam period of the Silurian age, and is found abundantly along the eastern part of the middle states, its range extending through the gold region of the southern states, north- ward, passing near Washington, Baltimore, and Philadelphia, thence crossing northern New Jersey, and to the south of the highlands across the Hudson, through western Massa- chusetts and Vermont into Canada. It also occurs at many localities to the eastward of this metamorphic range. It is very extensive- ly developed in the Tyrolese mountains, Aus- tria, and in various parts of Europe. A beau- tiful white dolomitic marble used by the ancient sculptors is found in the island of Tenedos, near the west coast of Asia Minor. A brown dolo- mite, the magnesian limestone of Tennant, oc- curs in the north of England in beds of con- siderable thickness, resting on the Newcastle coal formation. In the Isle of Man it is found in a limestone resting on graywacke, and it occurs in trap rock in Fifeshire. Columnar dolomite is found in metamorphic rocks in the Niagara group, in the upper Silurian formation in western New York, and in serpentine in Russia. For agricultural purposes magnesian lime is not as highly valued as pure lime. It enters less largely into the composition of most cultivated plants, and is thought to render the soil less friable. For making mortar there is a difference of opinion, the European masons rejecting it, while it is popular in the United States. As a building stone, dolomite ranks among the best, as it is easily worked and very durable. It is obtained in large blocks of sound and uniform texture, with good grain for split- ting, and unmixed with foreign matters. But different layers in the same quarry vary greatly in quality. The softness of the stone admits <>t' it- being easily sawn into ashlar and carved into ornamental mouldings. In England, dolo- mito has proved so durable and excellent, that a variety of it found at Bolsover moor was se- lected for the new houses of parliament. The choir of Southwell church, which was built of this variety of stone in the 12th century, was MARBLE OF ANALYZED BY Carbonate of lime. Carbonate oi magneita. Hastings, N.Y.. Sing Sing, " .. Tuckahoe, " .. Eoxbuiy,Vt.... J. W. Draper, M.D.. Lewis C. Beck, M.D. T.S.Hunt 52-82 53-24 61-75 53-90 45-78 45-89 88-25 44-04 DOLPHIN found by the commissioners to be in so perfect a state that " the mouldings and carved en- richments were as sharp as when first execu- ted." After describing other examples illus- trating the durability of this rock, the commis- sioners say : " As far as our observations ex- tend, in proportion as the stone employed in magnesian limestone buildings is crystalline, so does it appear to have resisted the decom- posing effects of the atmosphere ; a conclusion in accordance with the opinion of Professor Daniell, who has stated that, from the results of experiments, he is of opinion that ' the nearer the magnesian limestones approach to equiva- lent proportions of carbonate of lime and car- bonate of magnesia, the more crystalline and better they are in every respect.' " The fol- lowing analyses of some of the best of the American dolomites show how nearly they correspond in composition to the requisite of Professor Daniell : DOLPHIN (delphimu, Cuv.), a carnivorous cetacean mammal, found in most of the seas of the world. The dolphins, as generally re- stricted, have a convex forehead, and a beak or snout armed with teeth, separated from the forehead by a well marked furrow; they do not acquire the dimensions of the whales, be- ing rarely more than 9 ft. long. The body is fusiform in shape, without evident neck, and terminated by the horizontal tail common to all cetaceans; the head is not disproportion- ately large, and both jaws are toothed ; there are two pectoral fins, and toward the middle of the back is a fold of the skin which may be called a dorsal fin ; the eyes are small, with bare lids; the external opening of the ear is small ; the tongue is thick, soft, and but slightly movable ; the skin is naked and soft, covered only by a thick mucosity. The teeth are sim- ple, conical, and numerous, varying in number even in individuals of the same species. The cranium is very small compared with the face, concave, and much elevated in front and arched behind ; the snout is narrow and elongated from the prolongation of the maxillaries and intermaxillaries, which are not curved forward above; the upper jaw is a little shorter than the lower; the maxillaries extensively overlap the frontals ; the tubercles which represent the nasal bones are above the intermaxillaries, resting on the frontals ; the parietals are below the maxillaries, and quite on the side; the sym- physis of the lower jaw is extensive, and the bone is light and hollow. The cervical vertebra, seven in number, are very thin, and united; the dorsals are 13, with as many pairs of ribs, their articular processes becoming effaced by age, commencing posteriorly, and the trans-