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LEFT ROCKLAND 84 ROCKY MOUNTAINS banks, and several daily and weekly news- papers. The manufacture of lime is the principal industry. Near by are exten- sive quarries of fine granite of which the post-offices of New York and Cincinnati and the custom-house in St. Louis are built. Besides an immense lime industry Rockland has machine shops, foundries, iron and brass works, etc. Pop. (1910) 8,174; (1920) 8,109. ROCKLAND, a town of Massachusetts, in Plymouth co. It is on the New York, New Haven, and Hartford railroad. Its industries include the manufacture of shoes, nails, etc. There is a public library and other buildings. Pop. (1910) 6,928; (1920) 7,544. ROCK OF CHICKAMATJGA, a name applied to Gen. George H. Thomas, U. S. A., on account of his heroic stubbornness in holding his position at Chickamauga during the Civil War, in September, 1863. See Thomas, George H. ROCK PIGEON, a pigeon that builds its nest in hollows or crevices of rocks and cliffs, especially the Columba livia. ROCK RIVER, a river of the United States, which rises in Wisconsin, 50 miles W. of Lake Michigan, and falls into the Mississippi 2 miles below Rock Island city; length, 330 miles, about 225 of which have been ascended by small steam- boats. ROCK SALT, common salt, or chloride of sodium, occurring as a mineral and in a solid form. It is always mixed with various impurities. It is found massive or crystallized, its crystals generally cubes, its masses very often either granu- lar or fibrous. It is white, gray, or, ow- ing to the presence of impurities, more rarely red, violet, blue, or striped. For its chemical and other qualities, see Salt. It is a very extensively-diffused mineral, and in some places forms great rock and even mountain masses. A hill of rock- salt near Montserrat, in Spain, is 500 feet high. The island of Ormus, in the Per- sian Gulf, is formed of rock salt. The Indus, in the upper part of its course, forces its way through hills of rock salt. ROCK SCORPION (Buthus or Scorpio afer), a species of scorpion found in Af- rica, averaging about six inches in length. The bite of this animal, though not ab- solutely fatal, is yet considered to be dangerous. ROCK SNAKE, a name sometimes given to any individual of the genus Py- thon. Rock snakes are among the largest of living reptiles; specimens of 18 and 20 feet long have been brought to the United States. They kill their prey by constriction, and swallow it whole, com- mencing with the head. ROCK SPRINGS, a city of Wyoming, in Sweetwater co. It is on the Union Pacific railroad. In the neighborhood are important coal mines and it is also the center of an important farming and cattle raising region. The notable buildings in- clude a State hospital, government build- ing, public library, city hall, Elks' build- ing and a Masonic Temple. Pop. (1910) 5,778; (1920) 6,456. ROCKVILLE, a city of Connecticut, in Tolland co. It is on the Hockanum river, and on the New York, New Haven and Hartford railroad. Excellent water power is furnished by the river and the industrial establishments include woolen mills, silk mills, an envelope factory, etc. The city has an excellent school system and a public library. Pop. (1910) 7,977; (1920) 7,726. ROCKVILLE CENTRE, a village of New York in Nassau co. It is on the Long Island railroad. It is chiefly a resi- dential place but has important oyster fishing interests, and a lace and handker- chief factory. Its public institutions in- clude a public library and a Catholic parochial school. Pop. (1910) 3,667; (1920) 6,262. ROCKY MOUNT, a city of North Carolina, in Edgecomb and Nash counties, on the Atlantic Coast Line railroad. It is the center of an important cotton and tobacco growing region. Its industries include railroad repair shops, and manu- factures of tobacco, wood products, and hosiery. Pop. (1910) 8,051; (1920) 12,742. ROCKY MOUNTAINS, THE, a chain of mountains in the central and W. por- tions of the North American continent, are a prolongation of the great Mexican Cordillera, extending from the N. fron- tier of Mexico N. in several ranges, one of which, the E., passing through British North America, reaches the Arctic ocean in about lat. 70 N.; while the W., pass- ing near the Pacific coast, terminates near Prince William's Sound, in about lat. 60° N. The territory occupied extends from the Californian shores of the Pa- cific to about Ion. 105° W., or it may be considered as extending 125 miles further E., including the Black Hills of South Dakota and Wyoming. The whole area properly included by the mountains and their intervening valleys and desert lands in the country belonging to the United States is estimated at about 980,000 square miles. The mountainous belt of eastern New Mexico and of the State