IZ8 OF THE NATURE OF THE TIDES.

fere, the theory and facts will be found to agree.But it must be observed, that what has been heresaid, relates only to such places as lie open tolarge oceans. In seas and channels, which aremore confined, a number of causes concur,which occasion considerable deviations from thegeneral rule. Thus, it is high water at Ply-mouth about the sixth hour; at the Ifie of Wightabout the ninth hour; and at London-bridgeabout the fifteenth hour, after the moon haspassed the meridian. And at Batlha, in thekingdom of Tonquin, the sea ebbs and flowsbut once a day; the time of high water beingat the setting of the moon, and the time of lowwater at her rising. There are, also, great vari-ations in the height of the tides, according tothe situation of coasts, or the nature of theftreights which they have to pass through.Thus, the Mediterranean and Baltic seas havevery small elevations; while, at the port ofBristol, the height is sometimes forty feet j andat St. Malo’s it is said to be near a hundred.

What has been said of the ocean may likewisebe applied to the air; for the surface of the at-mosphere being nearer to the moon than thesurface of the sea, it is plain that the aerial tidesmust be much more considerable than those ofthe ocean : and on this account it should seemto follow, that the mercury in the barometerwould sink considerably lower than at other

4 times,