184 GREAT SLAVE LAKE 85 m. long and 100 ft. above the level of Great Salt lake is 26 m. S. E. of the latter, and flows into it through a river called the Jordan. Utah lake ahounds with fish. Bear river flows into the Great Salt lake from the north, and several smaller rivers from the east. The floods of spring spread the lake over large tracts, from which it recedes as summer advances. It was evidently once vastly more extensive than at present. The country around it is mostly des- olate and barren, though there are portions which irrigation would render very fertile. The water is transparent, but excessively salt ; it contains about 22 per cent, of chloride of sodium (common salt), slightly mixed with other salts, forming one of the purest and most concentrated brines in the world. Its specific gravity is 1-17. There are no fish in the lake, but several species of insects and a species of crustacean (artemia fertility have been found (see " United States Geological Survey of the Territories" for 1872, pp. 744-'5); and im- mense flocks of gulls, wild ducks, geese, and swans frequent its snores and islands. The water is so buoyant that a man may float in it at full length upon his back, having his head and neck, his legs to the knee, and both arms to the elbow, entirely out of water. If he as- sumes a sitting position, with the arms extend- ed, his shoulders will rise above the water. Swimming, however, is difficult from the ten- dency of the lower extremities to rise above the surface ; and the brine is so strong that it can- not be swallowed without danger of strangula- tion, while a particle of it in the eye causes in- tense pain. A bath in this water is refreshing and invigorating, though the body requires to be washed afterward in fresh water. The first mention of the Great Salt lake was by Baron La Hontan in 1689, who gathered from the Indians west of the Mississippi some vague notions of its existence. It was explored and described in 1843 by Fremont, who was the first to navi- gate its waters. A thorough survey was made in 1849-'50 by Capt. Howard Stansbury of the United States army, whose report of " An Expedition to the Valley of the Great Salt Lake" was printed at Washington by order of congress in 1852. Another edition was published at Philadelphia in 1855. "The City of the Great Salt Lake," commonly called Salt Lake City, is situated on the Jordan river, which connects Lake Utah with the Great Salt lake, about 7 m. S. of the latter. (See SALT LAKE CITY.) GREAT SLAVE LAKE (Fr. Lac de FEsclave), a large irregular sheet of water in a district of the same name in the northwest territories of Canada, between lat. 60 40' and 63 N., and Ion. 109 30' and 117 30' W. ; length from E. to W., 300 m. ; greatest breadth, 50 m. Its N. -h*r. 9 are steep and rough, and from them it receives the outlets of Aylmer and Artillery lakes. On the south it presents a less rugged bank, and is entered by a river of its own name, flowing N. for about 300 m. from the W. end GREBE of Lake Athabasca. It contains a number of islands, some of which are well wooded. For half the year it is frozen over. Mackenzie river connects it with the Arctic ocean. GREAVES, John, an English mathematician and antiquary, born in Hampshire in 1602, died in London, Oct. 8, 1652. He was edu- cated at Oxford, and in 1630 was chosen geo- metrical lecturer in Gresham college, London. After visiting Holland, France, and Italy, he embarked in 1637 for Constantinople, whence he went to Egypt to examine the pyramids, of which no satisfactory account had then been given, and in 1640 returned to England, bring- ing with him several Arabic, Persian, and Greek manuscripts, and a large collection of gems, coins, &c. Soon after his return he was appointed Savilian professor of astronomy at Oxford. In 1648, having been ejected from Oxford for royalism, he settled in London. He published a " Discourse on the Roman Foot and Denarius" (1647), wrote a Persian gram- mar, and partly compiled a Persian lexicon. A collection of his minor papers was published in two volumes in 1737. GREBE, a lobe-footed bird of the family co* lymbidce, and subfamily podicipinw, compri- sing the genera podiceps (Lath.) and podilym- bus (Lesson). The genus podiceps has a long, straight, and slender bill, the culm en slightly curved at the tip, which is sharp and entire, the sides compressed, and the nostrils longitu- dinal and in a short groove ; the wings short and pointed, the first and second quills the longest and slightly emarginated near the tips; tail short, a mere tuft of loose feathers ; tarsi shorter than the middle toe, much compressed, covered with scales serrated posteriorly ; toes long, lobed on the sides, and united by webs at the base; hind toe short and broadly lobed; nails short, broad, flat, and obtuse. More than 20 species are -described, in all parts of the world; they are usually seen in small flocks on the shores of fresh-water lakes and rivers and near the seacoast, and rarely on land, as the posterior position of the legs ren- ders it very difficult for them to walk ; they are excellent swimmers and expert divers, flying under water to a considerable depth in pursuit of fish ; they are generally short and rapid flyers, but during their migrations the flight is elevated and long sustained ; when alarmed, they hide among the reeds, or sink under wa- ter, leaving only the bill out, till the danger is over. The food consists of fish and aquatic animals and plants ; the nest is made of grasses, lined with down, attached to the reeds or float- ing ; the eggs are three or four in number. The American species vary much in size ; one of the largest is the crested grebe (P. cristatus. Lath.), 24 in. long, with an extent of wings or 33 ; the adult male has a blackish brown bill, about 2 in. long ; upper part of head and crest, nape and upper plumage, blackish brown ; the ruff, which birds of this genus have in the breeding season, is reddish brown ending in
