SEA, in a strict sense, signifies a large portion of water almost surrounded by land, as the Baltic and Mediterranean Seas; but it is frequently used for that vast body of water which encompasses the whole earth. See the articles GEOLOGY and PHYSICAL GEOGRAPHY.
Sea-Air is that part of the atmosphere which is above the sea. Sea-air has been found salubrious and beneficial in certain distempers. This may be owing to its containing a greater portion of oxygenous gas or vital air, and being less impregnated with noxious vapours, than the land. Dr Ingenhousz made several experiments to ascertain the salubrity of sea-air. By mixing equal measures of common air and nitrous air, he found that at Gravesend they occupied about 1.04, or one measure and ths of a measure; whereas on sea, about three miles from the mouth of the Thames, two measures of air, one of common and one of nitrous air, occupied from 0.91 to 0.94. He attempted a similar experiment on the middle of the channel between the English coast and Ostend; but the motion of the ship rendered it impracticable. He found that in rainy and windy weather the sea-air contained a smaller quantity of vital air than when the weather was calm. On the sea-shore at Ostend it occupied from 94 to 97; at Bruges he found it at 105, and at Antwerp 109. Dr Ingenhousz thus concludes his paper. "It appears, from these experiments, that the air at sea and close to it is in general purer and fitter for animal life than the air on the land, though it seems to be subject to the same inconstancy in its degree of purity with that of the land; so that we may now with more confidence send our patients labouring under consumptive disorders to the sea, or at least to places situated close to the sea, which have no marshes in their neighbourhood. It seems also probable that the air will in general be found much purer far from the land than near the shore, the former being never subject to be mixed with land-air."