Page:The American Cyclopædia (1879) Volume IV.djvu/213

CENTRAL CITY CENTRAL PROVINCES 205 CENTRAL CITY, a town and the capital of Gilpin co., Colorado, situated partly in the val- ley of a tributary of North Clear creek and partly on the slopes of the surrounding moun- tains, 39 m. W. of Denver; pop. in 1870, 2,360. It is irregularly but substantially built. Its site is 8,300 ft. above the level of the sea. The streets are narrow, and some of them steep and rugged. Being in the centre of an exceedingly rich gold-raining region, it is at once a depot of supply and a point of shipment. The bullion shipped in 1870 amounted to $1,650,000. The town has a United States land office and an assay office. There are two hotels, a miners' and mechanics' institute with a library of about 1,000 volumes, and Catholic, Methodist, and Episcopal churches, with the last of which is connected a parish school. The high school building is of stone, and cost $20,000. St. James library association has about 500 volumes. A daily and two weekly newspapers are published. There are a num- ber of quartz mills, and a national bank with a capital of $50,000. CENTRAL HEAT. Since the year 1740, when the first observations respecting the increase of heat encountered with the increased depth below the surface were made by M. Gensanne in the lead mines of Giromagny in S. Alsace, abundant data have been collected by scien- tific men in various parts of the world in sup- port of the theory that the interior of the earth is intensely hot. The deepest mines of Mexico, England, France, Germany, and other countries, and the deeper artesian wells, and the hot springs ascending from still deeper sources, all lead to this conclusion. The vol- canic fires add their testimony to the existence of intensely heated masses beneath the crust of the earth, and the vast extent of surface agitated when they are suppressed, and relieved by their outlet, seems to indicate an almost general diffusion of the liquid molten masses from which they spring. Not only is the heat found generally to increase with the depth, but the rate of this increase has in many instances been determined. It is found to vary in differ- ent countries, in some increasing two or three times more rapidly than in others. The ave- rage rate is estimated by Kupffer at 1 F. for every 37 English feet; and by Cordier at 1 for every 45 feet. These phenomena, all point- ing in one direction, have led to the conclusion that somewhere in the interior the materials of the globe must be in a state of the most intense heat ; and calculations have been made show- ing at what depth the rocks must all exist as liquid lava, at what the temperature of melted iron would be found, at what platinum would fuse, and at what various matters, solid at the surface, would be volatilized, but for the enor- mous pressure. This theory is controverted by Sir Charles Lyell, M. Poisson, and other emi- nent authorities, on these grounds : When sub- stances, as metals, are melted, their tempera- ture cannot be raised a single degree above the point of fusion so long as a piece of the mate- rial remains unmelted. The same principle is exemplified in the impossibility of raising water to a higher temperature than 32 F. so long as a fragment of ice remains in it. The principle may be applied to the solid crust of the earth, which could no more remain unchanged, re- posing upon the surface of a fluid heated many times above the temperature at which its ma- terials would melt, than a stratum of ice of the same thickness could remain in the same situa- tion exposed to the same proportional differ- ence of heat. The crust that forms upon lava as it cools cannot be instanced in disproof of this statement, for this only forms when the heat is so much reduced that ebullition has en- tirely ceased; if this be renewed, the crust soon disappears in the fluid. Were the crust of the globe the result of partial cooling from a state of primitive fluidity, the whole planet must first have cooled down to about the tem- perature of incipient fusion, and hence the enormous degrees of heat supposed cannot ex- ist within it. M. Poisson "imagines that if the globe ever passed from a liquid to a solid state by radiation of heat, the central nucleus must have begun to cool and consolidate first." Were the central portion fluid, tides would be perceived in the mass, sufficient to cause the surface to rise and fall every six hours ; but no such fluctuations are observed, even in a crater like that of Stromboli, which is supposed to connect with the great central ocean of lava. The phenomena that have given rise to the hypothesis of central heat do not absolutely require this theory to account for them. Local heat is without question generated by chemical changes taking place among the materials be- neath the surface. These give rise to electrical currents, of the power of which to disturb the surface we can form little idea; but judging from their effects upon the limited scale on which they come under our observation, it would seem quite as philosophical to refer to them the phenomena connecting distant vol- canic outbreaks and earthquakes, as to call in an aid so hypothetical as that of the molten fluidity of the central portion of the globe. CENTRAL PROVINCES, one of the eight large administrative departments into which British India was in 1872 divided, situated between lat. 18 and 24 N., and Ion. 77 and 83 E. They were formed into a chief commissioner- ship by royal decree of Nov. 2, 1861. At first they consisted of the province of Nagpore and its dependencies, and the districts of Saugor and Nerbudda; were enlarged in 1862 by the annexation of Sumbulpore and its dependen- cies ; and in 1872 contained an area of 112,561 sq. m., of which 84,162 were immediate Brit- ish possessions, while the remainder belonged to 15 native states. According to an official report presented to parliament in 1870 (" State- ment exhibiting the Moral and Material Pro- gress of India during the years 1868 and 1869," London, 1871), the population of the British