Now as the moon in moving round the centre of gravity between itself and the earth describes a much larger orbit than the earth describes round the same centre, it follows that the centrifugal motion on the side of the moon opposite to the earth must be much greater than the centrifugal motion of the side of the earth opposite to the moon round the same centre. And secondly, as the attraction of the earth exerted on the moon's surface next to the earth is much greater than the attraction of the moon exerted on the earth's surface, the tides on the lunar sea, (if such there be,) should be much greater than those of our ocean. Add to this that as the same face of the moon always is turned to the earth, the lunar tides must be permanent, and if the solid parts of the moon be spherical, must always cover the phasis next to us. But as there are evidently hills and vales and volcanos on this side of the moon, the consequence is that the moon has no ocean, or that it is frozen.] 65 2."NYMPHS! YOU adorn, in glossy volumes roll'd, The gaudy conch with azure, green, and gold. You round Echinus ray his arrowy mail, Give the keel'd Nautilus his oar and sail; Firm to his rock with silver cords suspend 70 The anchor'd Pinna, and his Cancer-friend; With worm-like beard his toothless lips array, And teach the unwieldy Sturgeon to betray.-- Ambush'd in weeds, or sepulcher'd in sands, In dread repose He waits the scaly bands, 75 Waves in red spires the living lures, and draws The unwary plunderers to his circling jaws, Eyes with grim joy the twinkling shoals beset, And clasps the quick inextricable net. You chase the warrior Shark, and cumberous Whale, 80 And guard the Mermaid in her briny vale; Feed the live petals of her insect-flowers, Her shell-wrack gardens, and her sea-fan bowers; With ores and gems adorn her coral cell, And drop a pearl in every gaping shell. [_The gaudy conch_. l. 66. The spiral form of many shells seem to have afforded a more frugal manner of covering the long tail of the fish with calcareous armour; since a single thin partition between the adjoining circles of the fish was sufficient to defend both surfaces, and thus much cretaceous matter is saved; and it is probable that from this spiral form they are better enabled to feel the vibrations of the element in which they exist. See note on Canto IV. l. 162. This cretaceous matter is formed by a mucous secretion from the skin of the fish, as is seen in crab-fish, and others which annually cast their shells, and is at first a soft mucous covering, (like that of a hen's egg, when it is laid a day or two too soon,) and which gradually hardens. This may also be seen in common shell snails, if a part of their shell be broken it becomes repaired in a similar manner with mucus, which by degrees hardens into shell.