SCYTHROPS, the channel-bill, in na tural history, a genus of birds of the or der Pica. Generic character : the bill large, convex, cultrated, furrowed at the sides, hooked at the tip ; nostrils round, naked at the base of the bill ; tongue can tilaginous, split at the point ; toes two be fore, and two behind ; tail of ten feathers. Of this genus only one species is known. This is an inhabitant of New South Wales, and is generally designated as the New 'South Wales channel•bird. Its size is that of a crow ; but its length is considera bly greater, measuring two feet seven inches. It is seldom seen, excepting in the morning and evening, generally in pairs, sometimes in very small flocks ; its noise resembles the screaming sound of alarm uttered by poultry in danger. It is migratory, and supposed to feed on the seeds of trees, on fruits, and the exuvie of beetles. The tail is sometimes unfolded like a fan, both during the flight and sit ting of the bird, and gives it an interest ing and dignified appearance. It appears not to be easily tameable ; but of the na ture, manners and habits of this bird, lit tle is at present ascertained.
SEA, is frequently used for that vast tract of water encompassing the whole earth ; but is more properly a part or di vision of these waters, and is better de fined, a lesser assemblage of water, which lies before, and washeth the coasts of some particular countries, from whence it is generally denominated, as the Irish Sea, the Mediterranean Sea, the Arabian Sea, &c.
What proportion the superficies of the sea bears to that of the land is not pre cisely known, though it is said to he somewhat more than two-thirds. As the waters of the earth must necessarily rice to the surface thereof. as being specifically lighter than the earth, it was necessary there should be large cavities therein, for receptacles to contain them, otherwise they would have overspread all the su perfi cies of the earth, and ao have render ed it utterly uninhabitable for terrestrial animals ; for the centre of the earth be ing the common centre of gra% ity ; and the nature of fluids being such, that they equally yield to equal powers ; and the power of attraction being every where equal at equal distances from the centre ; it follows, that the superficial parts of the water will every where conform them selves to an equidistant situation from the centre, and, consequently, will form the surface of a sphere, so far as they extend.
Hence, that the sea seems higher than the earth or land, results from the fallacy of vision, whereby all objects and the parts of land as well as sea, the further they are off from us, the higher they ap pear; the reason of all which is plain from optics: for it is well known, that the den ser any medium is, through which we behold objects, the greater is the refrac tion ; or the more their images appear above the horizontal level; also the great er quantity of the medium the raysspass through, the more will they be bent from their first direction ; on both these ac counts, the appearances of things remote, and on the sea, will be somewhat above the horizon, and the more so as they are the more remote.
With regard to the depth or profundity of the sea, Varenius affirms that it is in some places unfathomable, and in other places very various, bei ng in certan places ., 46 1 i 2 To 4i English miles, T Tba' lir' in other places deeper, and much less in baysthan in oceans In general the depths of the sea bear a great analogy to the height of mountains on the land, so far as Is hitherto discovered : and it is a general rule among sailors, and is found to hold true in many instances, that the more the shores of any place are steep and high, forming perpendicular cliffi, the deep er the sea is below ; and that, on the contrary, level shores denote shallow seas. Thus the deepest part of the Mediterra nean is generally allowed to be under the height of Malta. And the observation of the strata of earth and other fossils, on and near the shores, may serve to form a good judgment as to the materials to be found in its bottom. For the veins of salt and of bitumen doubtless run on the same, and in the same order, as we see them at land : and the strata of rocks that serve to support the earth of hills and ekvated places on shore, serve also, is the same continued chain to support • lie immense quantity of water in the basin of the sea.