The ease with which oil and water slide over each other is agreeably seen if a phial be about half filled with equal parts of oil and water, and made to oscillate suspended by a string, the upper surface of the oil and the lower one of the water will always keep smooth; but the agitation of the surfaces where the oil and water meet, is curious; for their specific gravities being not very different, and their friction on each other nothing, the highest side of the water, as the phial descends in its oscillation, having acquired a greater momentum than the lowest side (from its having descended further) would rise the highest on the ascending side of the oscillation, and thence pushes the then uppermost part of the water amongst the oil. NOTE XXX.--SHIP-WORM. _Meet fell Teredo, as he mines the keel With beaked head, and break his lips of steel._ CANTO III. l. 91. The Teredo, or ship-worm, has two calcareous jaws, hemispherical, flat before, and angular behind. The shell is taper, winding, penetrating ships and submarine wood, and was brought from India into Europe, Linnei System. Nat. p. 1267. The Tarieres, or sea-worms, attack and erode ships with such fury, and in such numbers, as often greatly to endanger them. It is said that our vessels have not known this new enemy above fifty years, that they were brought from the sea about the Antilles to our parts of the ocean, where they have increased prodigiously. They bore their passage in the direction of the fibres of the wood, which is their nourishment, and cannot return or pass obliquely, and thence when they come to a knot in the wood, or when two of them meet together with their stony mouths, they perish for want of food. In the years 1731 and 1732 the United Provinces were under a dreadful alarm concerning these insects, which had made great depredation on the piles which support the banks of Zeland, but it was happily discovered a few years afterwards that these insects had totally abandoned that island, (Dict Raisonne, art, Vers Rongeurs,) which might have been occasioned by their not being able to live in that latitude when the winter was rather severer than usual. NOTE XXXI.--MAELSTROM. _Turn the broad helm, the fluttering canvas urge From Maelstrom's fierce innavigable surge._ CANTO III. l. 93.