BITUMINOUS COAL-BITZIUS.

stances was by supposing that some 'volcanic' force acted on beds of bituminous coal. It is now abundantly illustrated in both hemispheres that the origin may be in unaltered strata of any age from Silurian up to Tertiary, at the ordinary temperatures of inconsiderable depths, time accomplishing the results that were once referred to volcanic

agency. The material required was doubtless organic, but it is a question how far the immense animal life of the geological past contributed to the result. Some animal fossils contain B. Inanumber of localities, there is reasonably a connection with bituminous shales, with a vegetable history, and largely found in rocks older than the Carboniferous. Mineral Caoutchouc or Elastic B., called Elaterite (CH2), is brown and flexible; one kind, like india-rubber, will erase pencil marks: one of the few places where it is found is a coal-mine near Southborough, Mass.

BITU'MINOUS COAL: varieties of coal which contain a large percentage of volatile matter. They yield, on their destructive distillation, considerable gas, remarkably pure and with good illuminating qualities, and are consequently largely used for that purpose. See COAL.

BITU'MINOUS LIMESTONES: limestones impregnated and sometimes deeply colored with bituminous matter, obtained from decaying vegetables, or, more probably, from the decomposed remains of those animals, the hard parts of which form so large an amount of the rock.

BITU'MINOUS SHALES: indurated beds of clay occurring in the coal-measures, and containing such an amount of carbon and volatile matter that they are able to keep up combustion when mixed with but a little coal. They are indeed impure coal, with a large percentage of ash or earthy matter, which after burning retains the original form. See COAL.

BITZIUS, bit'se-us, ALBERT (better known under the nom de plume of Jeremias Gotthelf): 1797, Oct. 4-1854, Oct. 22; b. Morat, canton of Freiburg, Switz.: author. He was educated for the church; and after holding several cures, was appointed, 1832, pastor of Lützelflüh, in Emmenthal, canton of Bern, which office he retained till his death. His first work was The Mirror of Peasants (Burgsdorf, 1836), he touching history of a poor villager, Jeremias Gotthelf, which pseudonym B. ever after retained. In 1838, appeared his Sorrows and Joys of a Schoolmaster; in 1839, Dursli, the Brandy-drinker, and How Five Maidens miserably perish perish in Brandy; in 1842-46, 1842 Scenes and Traditions of the Swiss, 6 vols., in which B. narrates, with great art, the old national legends, among which the most remarkable is the Reconciliation. The best and most popular of his stories, however, are Grandmother Katy (Berlin, 1848); Uli, the Farmservant (Berlin, 2d ed., 1850); its continuation, Uli, the Farmer (2d ed., Berlin, 1850); and Stories and Pictures of Popular Life in Switzerland (Berlin, 1851). Subsequently, he wrote several pamphlets against the extreme German democrats, without, however, violating those popular sym

BIURET-BIVALVE SHELLS.

pathies and liberal convictions which pervade his writings, and which at an earlier period led him vehemently to oppose the family government of the Bernese aristocracy. His last work was The Clergyman's Wife (1854). B.'s writings are greatly relished in Switzerland. They are characterized by simplicity, inventiveness, a wonderful fidelity in the delineation of manners and habits, great vigor of description, and raciness of humor. See his Life by Manuel (Berl. 1857), and Brockhaus (Berl. 1876).

BIURET, n. bi-ü'rět [bi, twice, and urea]: a chemical substance formed in the decomposition of urea.

BIVALVE, n. bi'vălo [F. bivalve-from L. bis, twice; valvæ, folding-doors]: a shell consisting of two parts which shut and open, as the mussel or oyster; in bot., a seed case or vessel which consists of two parts like a mussel. ADJ. also BIVALVULAR, a. -vu-ler, and BIVAL'vous, a. -vus, having two shells, as the oyster or mussel.

BI'VALVE SHELLS, or BIVALVES: testaceous coverings of mollusks, which consist of two concave plates or valves, united by a hinge. So long as molluscous animals, provided with shells, were considered by naturalists almost exclusively with respect to these, the order of Bivalve Shells, originally established by Aristotle, retained its place (see CONCHOLOGY); and indeed the external character upon which it is founded is closely connected with some of the important structural characters according to which mollusks are now classified. See MOLLUSCA. A vast majority of recent bivalve shells belong to Cuvier's Testaceous order of Acephalous Mollusca, the Lamellibranchiate (q.v.) Mollusca of Owen, although with them are classed some which were placed among Multivalves (q.v.) by conchologists, on account of accessory valves which they possess, and some which have a calcareous tube superadded to the true valves, or even taking their place as the chief covering of the animal. There are also animals of the class Brachiopoda (q.v.), or Palliobranchiata, which possess bivalve shells, as the Terebratula, or Lamp-shells (q.v.), etc. The structure of the shell, however, when closely examined, is found to be different in these two classes (see SHELL), although its general appearance is much the same. A very large proportion of the bivalve shells of the older fossiliferous rocks belong to the class Brachiopoda.

In the Brachiopoda, one valve is ventral, and the other dorsal; in the Lamellibranchiata, the one is applied to the right side, and the other to the left side of the animal. The valves of ordinary bivalve shells consists of layers, of which the outermost is always always the smallest; and each inner one extends a little beyond it, so that the shell becomes thicker and stronger as it increases in length and breadth. The valves are connected at the hinge by an elastic ligament; and in general this consists of two parts, more or less dis tinct-one on the outside, to which the name ligament is sometimes restricted, and which is stretched by the closing of the valves; another, sometimes called the spring, more in

BIVENTRAL-BIVOUAC.

ternal, which is compressed by the closing of the valves, and tends to open them when the compressing force of the adductor muscle or muscles is removed, the effect of which is to be seen in the gaping of the shell when the animal is dead. The hinge is often furnished with teeth which lock into each other; sometimes it is quite destitute of them; sometimes the hinge-line is curved, sometimes straight. Conchological classification has been much founded upon characters taken from this part. The valves of some bivalve shells are equal and symmetrical, in ot they are different from one anot

particularly in those mollusks which, like the oyster, attach themselves permanen permanently by one valve to some fixed substance, as a rock. Sometimes the valves of bivalve shells close completely at the pleasure of the animal; those of others always gape somewhere.

The point of the hinge, from which the formation of each valve has proceeded, is called the umbo. On the side of the umbo opposite to the ligament there is usually a small depression called the lunule. The marks, visible on the inside of a bivalve shell, are the impressions of the mantle of the (lamellibranchiate) mollusk, and of the adductor muscle or muscles.

BIVENTRAL, a. bi- věn'tral [L. bi, two; venter, belly]: in anat., having two bellies; as 'a biventral muscle.'

BIVIOUS, a. bi'vi-ŭs [L. bi, two; via, way]: going in two directions.

BIVOUAC, n. biv'wak [F. bivouac, a bivouac, guardfrom Ger. bei-wache, an additional watch: Sp. vivac, townguard]: the encampment of an army for the night in the open air, generally without tents: V. to take rest or refreshment in the open air, as an army on march, or travellers on a journey. BIV'OUACKING, imp. BIv'OUACKED, pp. wakt.

BIVOUAC: the encampment of soldiers in the open air, without tents, where every one remains dressed, and with his weapons by him. Even during the Seven Years' War it was no uncommon thing for the whole army, when in the vicinity of the enemy, to pass the night in their ranks, each lying down in his place, in order to be ready to stand to their arms at a moment's notice. But the French revolutionary armies introduced the practice of dispensing with tents altogether, and regularly passing the night en bivouac. Hence, in a great measure, that rapidity in their motions which long made them uniformly successful; and the practice was afterwards imitated by the other armies of Europe, though less by the English. Soldiers in B. light fires, and improvise, where it is po possible, huts of straw, branches, etc. But this mode of encampment, though favorable to celerity

Several Forms of Bivalves: a, Avicula; B, Pectunculus, with extended foot (a); C, Venus, with respiratory siphons (a, b,) and extended foot (c); D, Mya truncata, showing respiratory siphons (a, b,) and foot (c).