SEA-waTEn.—For an accurate knowledge of the composition of sea-water, we are mainly indebted to the investigations of prof. Forchhammer of Copenhagen. Not very many years ago, the only elements known to exist in sea-water, in addition to those constituting water itself, were chlorine, iodine, bromine, sulphur, carbon, sodium, magnesium, potassium, calcium, and iron. To these twelve must now be added (18) fluorine, discovered by Dr. George Wilson; (14) phosphorus, as phosphate of lime; (15) nitrogen, as ammonia; (16) silicon, as silica, in which form it is largely collected by sponges from sea-water; (17) boron, as boracic acid; (18) silver; (19) copper; (20) lend; (21) zinc; (22) cobalt; (23) nickel: (24) manganese; (25) aluminium, as alumina; (2(i) strontium, as strontia; (27) barium, as baryta. Several of these elements, however, exist in such small quantities that they can only be discovered indirectly, that is to say, in sea-weeds, marine animals, or in the stony matter deposited at the bottom of the boilers of oceanic steamers. The substances which, in respect of quantity, play the principal part in the composition of sea-water are chlorine, sulphuric acid, soda. potash, lime, and magnesia; those which occur in less but still determinable quantity, are silica, phosphoric acid, carbonic acid, and oxide of iron. In the elaborate tables which are annexed to this paper. Forchhammer has always calculated the single substances (chlorine, sulphuric acid, magnesia, lime, and potash) and the whole quantity of salt for 1000 parts of sea-water; but besides this, he has calculated the proportion between the different substances detennined, referred to chlorine = 100, and of all the salts likewise th It referred to chlorine. This last number is found we the sum of all the salts found in 1000 parts of any sea-water by the quantity of chlorine found in it; and he terms it the of that sample of sea-water.* This chemist divides the sea into seventeen regions, his reasons for doing so being that he could avoid the prevailing influence which those parts of the ocean which arc best known, and front which 1 as n whi h he taken most observations, would exert upon the calculations of the mean number for the whole ocean. In reference to the salt n it y of the surface of the ocean, lie has made the following observations, (1.) The mean salinity of the Atlantic between 0° and 30° n.
sat. is 36.169 (i.e., this is the quantity of salts in 1000 parts of water); the maximum, which is also the maximum of the surface-water of the whole Atlantic, being 37.908, and occurring in 24° 13' n. lat., and about 5° w. from the coast of Africa, where no rivers of any size carry water from the land, and where the influence of the dry and hot winds of the Sahara is prevailing. This maximum is equal to the mean salinity of the Mediterranean, and is only exceeded by the maximum of that sea off the Libyan desert, and that of the Red sea. The minimum is 34.283 in 4° 10' s. lat., and 5° 36' w. long-, close to the coast of Africa, where the large masses of fresh water which the great rivers of that region pour into the ocean exercise their influence. (2.) In the Atlantic, between 30' n. lat. and a lice drawn from the n. point of Scotland to the n. point of Newfound land, the mean salinity is 35.946, the diminution being due to the fresh water poured into it by the southern mouth of the St. Lawrence. (3.) In the Baffin's bay and Davis's strait region, the mean salinity is 33.281. and the salinity increases from lat. 64° toward the n., being in 64°, 32.926, and in 69°, 33.598. This peculiarity is owing (says Foreh hammer) to the powerful current from the Parry islands, which through different sounds passes into Baffin's bay, where it is mixed with the great quantity of fresh water that comes into the sea from the West Greenland glaciers. Had this fact been known before the sounds that connect the Parry archipelago with Baffin's bay were discovered, it might have proved the existence of these sounds, because bays and inlets show quite the reverse; the further we get into them, the less'saline the water becomes. (4.) From , eleven observations on the Mediterranean between the straits of Gibraltar and the Greek archipelago, he confirms the old view of its great salinity; its mean salinity being 37.936, while that of the whole ocean is 34.388. Its maximum between the island of Camila and the African shore; and•its minimum (36.301) is at the straits of Gibraltar. These results are due to the influence of Africa and its hot and dry winds. In salinity, the Mediterranean is only exceeded by the Red sea, whose mean salinity is 43.067. (5.) 'The Black sea, like the Baltic, is a mixture of salt and fresh waters. In three different experiments, the 'salinity varied from 18.146 to 11.880. At a distance of 50 m. from the Bosphorus, the proportions between chlorine, sulphuric acid, lime, and magnesia, were 100 : 11.71 : 4.22 : 12.64, while the normal oceanic proportions are 100 : 11.89 : 2.96;
11.07; thus sheaving a relative increase in the lime and magnesia. (6.) As the Caspian sea is considered by many geologists to have been formerly in connection with the Black sea, the results of Mahner's analysis of its waters are given. The salinity varied between and 6.236, and the proportion between the chlorine, sulphuric acid, lime, and magnesia, is 100 : 44.91 : 9.34 : 21.48, which differs extremely from the normal pro portion. Thus the Caspian sea, if it ever had any connection with the Black sea, must have entirely changed its character since that time—a change which might be Occasioned by the different salts which the rivers brought into it, and which accumulated there by evaporation of the water; or which might be caused by the deposition of different salts in the basin of the Caspian sea itself. (7.) The Atlantic between 30° s. lat. and a line from cape Horn to the cape of Good Hope, is less saline than the corresponding region n. of the equator; and all the samples from the western part of this region have less, while the samples from the eastern part, nearer to the African coast, have considerably more sulphuric acid than the normal quantity. Does this, asks Forchhammer, depend upon the more volcanic nature of the w. coast of Africa than the e. American coast? (8.) In the sea between Africa and the East India islands, the mean salinity is 33.868. The minimum (25.879) is from a place high up in the bay of Bengal, and of course much influenced by the Ganges. It lies, however, about 300 m. from the mouth of that river; and another specimen taken60 m. nearer the mouth has a salinity of 32.365, so that it would seem as if, some other cause (possibly fresh-water springs at the bottom) had been in operation to weaken the sea-water at the minimum spot. (9.)'In the Patagonian cold-water current, the mean salinity was 33.966; while three samples brought from the South Polar sea, by the late sir James Ross, had different salinities of and 37.513. Forchhammer cannot account for these discrepancies. All the specimens showed a great excess of sulphuric acid (12.47 in place of 11.88, as compared with 100 of chlorine), a result probably due to the volcanic nature of the antarctic continent. Forchhammer's analyses of waters-from other of his 17 districts call for no remark; and the following are the general results of his investigations. "If we except the North sea, the Kattctrat, Sound, and Baltic, the Mediterranean and Black sea, the Caribbean sea and the Red sea, which have all the characters of bays of the great ocean, the mean numbers are the following: Chlorine. Lime. Magnesia. 1000 18.999 2.258 0.556 2.096 24.404 1.812 100 11.88 2.93 11.03 Equivalents, 429 45 16 82 Thus it is evident that the sea-water, in its totality, is as little a chemical compound as the atmospheric air; that it is composed of solutions of different chemical compounds; that it is neutral, because it everywhere in the atmosphere finds carbonic acid to neutral ize its bases. and everywhere on its bbttom and shores finds carbonate of lime to neutral ize any prevailing strong acid; that, lastly, the great stability of its composition depends upon its enormous mass, and its constant motion, which occasions that any local varia Lion Is evanescent compared to the whole quantity of salt." It will be seen that the Atlantic is that part of ocean which contains the greatest proportion of salt, while some of the bays in the tropical or subtropical zone (the Mediterranean and Red sea, for example) have a greater mean than the Atlantic; that on approaching the shores. the sea-n cler, us might have been expected, becomes more diluted, and consequently less saline; that the polar currents contain less salt than the equatorial; that the polar current of west Greenland contains more sulphuric acid that the water in any other region except the east Greenland and south polar currents (while in the ocean at large the chlorine is to the sulphuric acid as 100 :11.89; in the south polar current it is as 100 :12.55). As in the case of the west. Greenland current, there is no neighboring vol canic region to account for this excess. Forchhammer s. i suggests that the absence of fueoidal plants, which have a great attraction for sulphuric acid, may have an nflu ence in bringing about this result;* that most lime occurs in the ocean in the second region, the middle part of the nOrthern Atlantic; and the least in the west Greenland polar current (the quantities being 3.07 and 2.77 respectively). Wherever, in other regions, the influence of land prevails, the lime also is in excess; thus, the Black sea, it was 4.221.