COAL OIL 33 COAST DEFENSE aqueous vapor. The escape of coal gas from pipes into the soil is very injurious to the roots of trees and shrubs. The admixture of a very small quantity of air greatly impairs the illuminating power of coal gas. Three causes are capable of decreasing the luminosity of flame, viz.: (1) withdrawal of heat; (2) dilution; and (3) oxidation of luminous material. See Gas. Poisoning by coal gas, is known only as an accident. Occasionally sudden fatal consequences ensue among workmen from exposure to a sudden rush of un- diluted gas from gasometers and mains. More commonly, slowly fatal cases result from the gas-tap in a bedroom being left open carelessly, from accidental extinc- tion of the light, from blowing the gas out, or from leakage of the pipes in a house, or at a distance, the gas gaining entrance to the house in the latter case through cellars, walls, and more especial- ly by means of drains and sewer-pipes. COAL OIL, a name sometimes given to Petroleum (q. v.). COAL TAR, tar produced in the de- structive distillation of bituminous coal. It is a thick, sticky, dai'k-colored sub- stance, and is used in the manufacture of printers' ink, for asphalt pavements, coating ships, etc. The composition of coal tar varies according to the tempera- ture at which the coal is distilled, the higher the temperature the larger being the yield of solid bodies. Coal tar when distilled first gives off gas, then water containing ammoniacal salts, then a brown light oil which, when purified, is called coal-naphtha ; at higher tempera- tures a yellow, heavy, foetid oil called dead-oil, or creosote oil, then naphtha- lene; afterward the black residue in the retort solidifies on cooling and forms pitch, which is used to form asphalt, and a black varnish to protect iron from rust. If the distillation is continued, the pitch yields a yellow substance like butter, con- taining anthracene, phenanthrene, fluo- rene; afterward, at red heat, a bright orange powder, consisting chiefly of py- rene CieHio and chrysene Ci-,H,..; the resi- due forms a hard, porous coke. Coal tar colors are dyes prepared from aniline, naphthalene, phenol, and other com- pounds contained in coal tar. See Dye- ing. COAL TAR COLORS. See Dyeing. COAN, TITUS (ko'an), an American missionary; born in Killingworth, Conn., Feb. 1, 1801. After spending several months (1833-1834) on a dangerous ex- ploring expedition in Patagonia, he went to the Sandwich Islands (1835), occupy- ing the Hilo station 47 years, and in that ulf Stream and off from them ; and gi'avity re- of heights by of geographical time converting 14,000 natives. He wrote: "Adventures in Patagonia" (1880); "Life in Hawaii" (1881). He died at Hilo, Hawaii, Dec. 1, 1882. COANZA, or KUANZA, a river of Portuguese West Africa, flows generally N. W., and enters the Atlantic about 30 miles S. of St. Paul de Loando, by a mouth over a mile broad. It is naviga- ble for light vessels as far as the Cam- bambe cataracts, over 120 miles. COAST AND GEODETIC SURVEY, UNITED STATES, a bureau of the De- partment of Commerce, charged with the survey of the Atlantic, Gulf, and Pacific coasts of the United States, including the coast of Alaska; the survey of rivers to the head of tidewater or ship navigation; deep-sea soundings, temperature and cur- rent observations along the said coasts and throughout the C Japan Stream flowing magnetic observations search; determination geodetic leveling, and positions by lines of transcontinental trl angulation, which with other connecting triangulations and observations for lati- tude, longitude, and azimuth, furnish points of reference for State surveys and connect the work on the Atlantic coast with that on the Pacific. Results of the survey are published in the form of an- nual reports, which include professional papers of value; bulletins which give in- formation deemed important for imme- diate publication; notices to mariners, issued monthly; tide tables, issued an- nually; charts upon various scales, in- cluding harbor charts, general charts of the coast, and sailing charts; chart cata- logues and "Coast Pilots." COAST ARTILLERY. See ARTILLERY. COAST DEFENSE, a system of forti- fications to protect a country from hostile attacks or occupations on its coast lines. It consists of forts well equipped with heavy guns and thoroughly manned and placed at strategic points. It includes also torpedo boats, submarines, harbor mines, searchlights, and all the other adjuncts that make the work of the forts effective. The extensive coast line of the United States has required a great ex- penditure of money, planning, and in- genuity in order to secure the country's safety in time of war. Adequate atten- tion had not been given to this important work before the outbreak of the World War; but the lessons taught by that great conflict have stimulated the "energy of the navy depai'tment and the liberal- ity of Congress. All ports of commer- cial or strategic value along both coasts of the United States have now been
