ORANGE River, a large river of Southern Africa, which derives its origin from the waters of the Snowy Mountains, in the district of Graaf-Reynet, nearly at the north-eastern extremity of the colony of the Cape of Good Hope. It is formed chiefly by two rivers, the Ky Gariep or Yellow River, and the Nu Gariep or Black River, which unite their waters in latitude 29. 4., upwards of five hundred miles due east from their mouth. The latter branch, flowingfrom the south-east, is called, higher up, the Cradock River, and receives the Sea-Cow River and some other streams from the Sneuwbergen. The Muddy or Alexander River, flowing also from the south-east, falls into the Yellow River above its confluence with the Nu Gariep. The former river, the Ky Gariep, comes from the north-east, and is formed by the union of the Vaal River with the Hart stream or Malalareen. After the junction of these two streams, the Orange River flows at first in a north-westerly course, but afterwards bends to almost due west, which bearing it maintains until it falls into the Atlantic in latitude 28. 30. north. In the eastern part of its course it forms the limit between the territory of the Hottentots and that of the Boshuanas; the country on the south presenting an entirely different character of animal and vegetable life from that on the north. In its westerly course this river winds its way through a desert of a clayey or swampy character; the sandstone rocks rising in perpendicular walls, which are often prolonged to a vast extent. The country retains the same aspect for a considerable space on both sides of the river; and the heat is here very great and oppressive. The course of the Orange River, including its windings, must considerably exceed one thousand miles.

Orange, Sea, in Natural History, a name given by Count Marsigli to a very remarkable species of marine substance, which he denominates a plant. It is tough and firm in its structure, and in many things resembles the common fucus; but instead of growing in the branched form which the generality of these substances assume, it is round and hollow, and in every respect resembles the shape of an orange. It has, by way of root, some exceedingly fine filaments, which fasten themselves to the rocks, or to shells, stones, or any thing else that comes in the way. F rom these there grows no pedicle; but the body of the orange, as it is called, is fastened by them to the rock, or other solid substance. The orange itself is usually about three or four inches in diameter; and whilst in the sea it is full of water, which it retains even when taken up. In this state it frequently weighs a pound and a half; but when the water is let out, and it is dried, it becomes a mere membrane, weighing scarcely any thing. It is best preserved by stuffing it with cotton as soon as the water is let out of it, and then hanging it up to dry. Its surface is irregular and rough, and its colour is a dusky green on the outside, and a clearer but somewhat bluish green within; and its thickness is about an eighth part of an inch. When viewed by the microscope, it is observed to be all over covered with small glandules, or rather composed of them; for they stand so thick one by another, as to leave no space between, and seem to constitute the whole substance; so that it appears very like the rough shagreen skin used to cover toys. These are indeed so many hollow ducts, through which the sea-water finds a passage into the globe formed by this skin, and by this means it is kept always full and distended. On cutting it with a pair of scissors, the water immediately runs out, and the skins collapse; but there is something extremely remarkable in this, for the whole substance, near the wounded place, is in motion, and seems as if alive, and sensible of the wound. The glandules are found full of water, resembling small transparent bottles; and what goes to the structure of the plant besides these, is an assemblage of a vast number of filaments, all of which are likewise hollow, being filled with a clear and transparent fluid.