GRAPHITE. 143 GRAPTOLITE. which consumes the larger part of the product, the grapliile has to be mixed with chiy and sand. Eeeently the substitution of a mixture of graph- ite and grease for red lead has met willi much success. Since graphite, as it occurs in nature, is always mixed with other minerals, the material after being mined is crushed, and tlicn put through some kind of cleaning or concentration process. The separation is done either by means of an air-eurrent or water, preferably the latter. In 1898 the manufacture of artificial graphite from coke was begun at Niagara Falls, and in the year of its discovery 200,000 pounds of car- bon rods were graphitized in the electric furnaces, while in 1900 the production had risen to 860,- 750 pounds. It is said that the artificial product is fully equal to the natural material in its electrical conductivity, for use as a lubricant, and in the manufacture of stove-polish or lead pencils. Although the production of graphite in the United States has been increasing almost every year, still the amount produced is far from sufficient to supply the domestic demand. The imports therefore continue to be large. In 1897 the imports were 19,114,000 pounds, valued at $270,952, and in 1900 they were 32,299,000 pounds, valued at $1,390,141. The production of the United States for the same years was 3.393,000 pounds ($56,091), and 6,193,000 pounds ($172,762), respectively. Bibliography. Newberry, "The Origin of Graphite." in f<chonl of j/tnes Quarterlfi. vol. viii. (New York. 1887) ; Dawson, "On the Graph- ite of the Laurentian, in Canada," in Quarterhj Journal of the Geolofiical Society of Loiulon, vol. xxvi. (London, 1870) ; Postlethwaite, "On the Formation of Graphite in Contact Meta- morphism," in American Journal of Science, vol, xii. (New Haven, 1S91); Downs, "Occurrence, Treatment, and Application of Graphite," series of articles in the Iron Age (New York, 1900) ; Weinschenk, Zur Kennfniss der Graphitlaffer- sliitten (JIunich, 1897). For statistics of pro- duction and notes in regard to the trade, consult The Mineral Industri/, vols. i. to X. (New York, 1893-1902). GRAPHOPHONE (from Gk. ■ypa<ti^, graphs, writing -f ^mviJ, plione, voice). A machine for reproducing human speech and other sounds, in- vented by Charles S. Tainter and Chichester A. Bell. Its principle is the same as that of the phonograph (q.v.) of Edison, but it differs in mechanical details, and in employing a wax- coated cylinder of pasteboard instead of an all- wax cylinder. GRAPHOTYPE (from Gk.ypa^Tj, graph? . writ- ing + TvTToctt/pos, type). A process for produc- ing illustrations using an engraved surface, from which printing can he effected on an ordinary press. Drawings are made on a zinc plate covered with finely powdered French chalk, brought to a hard, firm surface by great pressure. The picture is drawn with a camel's-hair brush and an ink made of glue and lampblack. The uninked portion is then rubbed away and an electrotype made of the picture. This method was only partially success- ful, and has been superseded by other and more modem processes. GRAPNEIj. See Anchoe. GRAPTOLITE, grap't6-llt (from Gk. ypawTor, graptos, written, marked -j- ?.iSof, lithos, stone). A class of extinct animals, allied to the hydrozoa, fossil remains of which are foind in the lower Paleozoic rocks, especially in tho.se of Upper Cambrian, Ordovician, and Silurian age. The group derives its name from the likeness of its members to pencil markings on the rocks. They are found most abundantly in black shale forma- tions, and they are of grejxt importance to the geologists because of their nimu>rous species, that follow each other in rapid evolutional series through successively higher formations. Because of these lines of descent and the wide distribution of the species, graptolites are ideal horizon-mark- ers or index fossils in the lower Paleozoic rocks. The graptolites are delicate hydrnidlike col- onies growing from a miiuite embryonal polyp that was incased in a chitinous theca or cell, called the 'sicula.' From this sicula grew, by budding, a series of zoijids or individuals, the form of which is still recognizable in that of their fossilized chitinous coverings, the thecoe. Refined methods of isolation and decoloration of the graptolite colonies have been developed by Holm and Wiman, and have enabled these ob- servers to remove the colonies bodily from the inclosing rock, and section them in a microtome after much the same methods employed in his- tology. In this way the structure of the grapto- lite colonies has been shown to be much more complicated than had been suspected. This is especially true of the first group, the Dendroidea, to which belong sessile colonies with the forms of miniature trees (Dendrograptus) or of woven baskets (Dictyonema) (q.v.). In these Den- droidea three different forms of thecae have been found, viz.: Theca; proper, or nourishing indi- viduals ; alternating canals, considered by Wiman as gonangia or reproductive individuals ; and gemmating or budding individuals. Other au- thors, as Freeh, held the alternating canals to have been neinatophores. See Hydroids. The second group. Graptoloidea, consists of the older Dichograptidse and the younger Diplograp- tidae. In the former there grow, by successive forkings, from the sicula or embryonal cell, which is centrally situated, more or less numerous branches, each of which grows distall.v (at its extremity) and consists of a single series of thecae proper. This family, which begins in the upper Cambrian and does not extend beyond the Ordo- vician, exhibits a mo.st remarkable evolution from irregular many -branched forms (Clonograp- tus) to symmetrical forms with eight branches (Dichograptus), then to four-branched forms (Tetragraptus). and finally to biramous species (Didymograptus), with which last the family becomes extinct. An aberrant side line from this family is the genus Phyllograptus, in which the four branches of Tetragraptus become united along their dorsal sides to form colonies with cross-shaped sections. The younger Diplograptidoe, of which the type genus is Diplograptus, possess a central disk which apparently was a 'float,' and which bore a circle of reproductive sacs (gonangia ) , containing siculoc and numerous stipes (hydrorhabds) . The latter are biserial in Diplograptus, each being borne on a long stem (hydrocaule) , with a sicula at its farther end, from which the cells grow backward along the stem. The latter form3 hence an axis within the stipe, wherefore Diplo- graptus and its allies have been separated, aa
