Page:The American Cyclopædia (1879) Volume XII.djvu/586

572 OCEAN great system, and are kept of nearly uniform composition, notwithstanding numerous local causes of change, chiefly by means of great currents which circulate through them. Some of these currents are of vast extent, spread- ing over a large part of the oceans to which they belong, and with but slight variations they move without cessation in the great sys- tem of the circulation of the waters. A prin- cipal characteristic of the water of the ocean is its saltness. This is owing to various saline matters, prominent among which are chlorides, chiefly chloride of sodium or common salt. There are several sulphates, carbonates, iodides, and bromides, all the saline matter forming it in solution. Prof. Henry Wurtz suggested in the " American Journal of Mining" in 1868 that gold be sought for in sea water, and Son- stadt has since found a little less than one grain to the ton of water, held in solution by iodide of calcium. Silver deposited on the old cop- pering of ships has been extracted in quanti- ties sufficient to make its separation profitable, and it has been computed that the whole ocean holds in solution about 2,000,000 tons of silver. A more exact analysis will be given in the ar- ticle WATER. The proportion of salt varies in different places, sometimes exceeding 4 per cent. It is large where the water is deepest, but does not increase with the depth. Though inland seas generally contain less salt, the Med- iterranean contains more of it than the ocean itself; the specific gravity of its water east of the straits of Gibraltar has been found to be 1-0338, while that of water from the ocean west of the straits was 1-0294. The specific gravity of sea water near the equator is about 1-0277. Prof. Forchhammer of the university of Copenhagen, between the years 1840 and 1864, made numerous analyses of sea water from various parts of the globe, and embodied his investigations in a communication which appeared in the " Philosophical Transactions " of London for 1865. He found that the polar currents contain less salt than the equatorial, and that the proportion of saline matter in the Mediterranean was 3-793 per cent. ; in the Ca- ribbean sea, 3-610 ; and in the Red sea, 4-306. He divided the whole ocean into 17 regions, from each of which he made numerous analy- ses. The saline elements of the water may be derived from geological formations consisting in great part of such elements; but strata of this character always bear evidence of being deposited from ancient oceans, so that this de- rivation throws no light upon the real source of the salt. In different parts of the ocean various substances introduced by great rivers modify locally the composition of its waters ; and from the strata beneath the sea there no doubt emanate mineral springs, such as appear upon the land. Springs of fresh water are known in many places to rise up through the salt water, and some of them even furnish sup- plies to vessels. It is supposed that the devel- opment of animal life, particularly the forma- tion of coral, tends to preserve the equableness of the salinity of the ocean, and also its purity. (See CORAL.) The color of the sea, commonly described as bluish green, is by no means uni- form, and the causes of the changes of its hue have until recently been unexplained. In the tropics it is at one time an indigo blue, then a deep green; and upon some coasts a reddish or purplish hue is observed. The cause of the color is now regarded as depending on the ac- tion of suspended particles of solid matter on the light which traverses the water. Light on entering the water is refracted, and therefore more or less resolved into its primary colors, especially if the water is of sufficient depth. The red, orange, and yellow rays do not pene- trate the water to so great a depth as the blue and violet. Now the presence of minute solid particles causes some of the light after enter- ing the water to be reflected, and the color of this reflected light will depend upon the depth at which the reflection takes place. If the particles are large and freely reflect from a moderate depth, they will also prevent reflec- tion from a greater depth, so that the rays coming to the eye of the observer will be green ; but if the particles in the upper strata are minute and the reflection is from a con- siderable depth, the color will be more nearly a pure blue. The subject was experimentally examined by Prof. Tyndall while making a voyage in a steamer. His assistant cast a white plate attached to a cord into the water to a moderate depth, and when it reached the proper point of observation its color was green, although that of the water was blue. The phosphorescence of the sea is another of its characteristics. This varies under different circumstances, and is owing to the presence of myriads of invertebrate animals, some of which are microscopic, while others are of consid- erable size, as the jelly fishes. In the fiords on the coast of Norway the crystal clearness of the water is wonderful ; at the depth of 20 or 25 fathoms small objects may be discerned upon the sandy bottom, apparently magnified by the water itself. The depth of the ocean is very uncertain, and has been greatly over- rated. The difficulties of deep-sea soundings are referred to in the article ATLANTIC OCEAN. With reference to organic life at various depths, see DREDGING (DEEP-SEA). The extent of the surface of the ocean is estimated to be about 146,000,000 sq. m., or nearly three fourths of the whole earth's surface. OCEAN, an E. county of New Jersey, border- ing on the Atlantic, and drained by Metetecunk and Toms rivers and several creeks ; area, about 550 sq. m. ; pop. in 1870, 13,628. A sand beach from % to 1 m. wide extends along the coast, and between it and the mainland are two lagoons, Barnegat bay and Little Egg Harbor inlet. The surface is level, and much of it covered with pine forests ; the soil is light and sandy. Iron is found and manufactured in