Other streams of cold water arise from beneath the snow on the Alps and Andes, and other high mountains, which is perpetualy thawing at its under surface by the common heat of the earth, and gives rise to large rivers. For the origin of warm springs see note on Fucus, Vol. II. NOTE XXVII.--SHELL FISH. _You round Echinus ray his arrowy mail, Give the keel'd Nautilus his oar and sail. Firm to his rock with silver cords suspend The anchored Pinna, and his Cancer-friend_. CANTO III. l. 67. The armour of the Echinus, or Sea-hedge Hog, consists generally of moveable spines; (_Linnei System. Nat._ Vol. I. p. 1102.) and in that respect resembles the armour of the land animal of the same name. The irregular protuberances on other sea-shells, as on some species of the Purpura, and Murex, serve them as a fortification against the attacks of their enemies. It is said that this animal foresees tempestuous weather, and sinking to the bottom of the sea adheres firmly to sea-plants, or other bodies by means of a substance which resembles the horns of snails. Above twelve hundred of these fillets have been counted by which this animal fixes itself; and when afloat, it contracts these fillets between the bases of its points, the number of which often amounts to two thousand. Dict raisonne. art. Oursin. de mer. There is a kind of Nautilus, called by Linneus, Argonauta, whose shell has but one cell; of this animal Pliny affirms, that having exonerated its shell by throwing out the water, it swims upon the surface, extending a web of wonderful tenuity, and bending back two of its arms and rowing with the rest, makes a sail, and at length receiving the water dives again. Plin. IX. 29. Linneus adds to his description of this animal, that like the Crab Diogenes or Bernhard, it occupies a house not its own, as it is not connected to its shell, and is therefore foreign to it; who could have given credit to this if it had not been attested by so many who have with their own eyes seen this argonaut in the act of sailing? Syst. Nat p. 1161. The Nautilus, properly so named by Linneus, has a shell consisting of many chambers, of which cups are made in the East with beautiful painting and carving on the mother-pearl. The animal is said to inhabit only the uppermost or open chamber, which is larger than the rest; and that the rest remain empty except that the pipe, or siphunculus, which communicates from one to the other of them is filled with an appendage of the animal like a gut or string. Mr. Hook in his Philos. Exper. p. 306, imagines this to be a dilatable or compressible tube, like the air- bladders of fish, and that by contracting or permitting it to expand, it renders its shell boyant or the contrary. See Note on Ulva, Vol. II.