Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/425

 no cause of ebbing and flowing, save onely by the participation of another Sea, wherewith it hath communication, that is subject to great commotions.

In the fourth place we shall very easily find out the reason why the fluxes and refluxes are greatest, as to the waters rising and falling in the utmost extremities of Gulphs, and least in the intermediate parts; as daily experience sheweth here in Venice, lying in the farther end of the Adriatick Sea, where that difference commonly amounts to five or six feet; but in the places of the Mediterrane, far distant from the extreams, that mutation is very small, as in the Isles of Corsica and Sardinnia, and in the Strands of Rome and Ligorne, where it exceeds not half a foot; we shall understand also, why on the contrary, where the risings and fallings are small, the courses and recourses are great: I say it is an easie thing to understand the causes of these accidents, seeing that we meet with many manifest occurrences of the same nature in every kind of Vessel by us artificially composed, in which the same effects are observed naturally to follow upon our moving it unevenly, that is, one while faster, and another while flower.

Moreover, considering in the fifth place, that the same quantity of Water being moved, though but gently, in a spatious Channel, comming afterwards to go through a narrow passage, will of necessity run, with great violence, we shall not finde it hard to comprehend the cause of the great Currents that are made in the narrow Channel that separateth Calabria from Sicilia: for that all the Waters that, by the spaciousnesse of the Isle, and by the Ionick Gulph, happens to be pent in the Eastern part of the Sea, though it do in that, by reason of its largeness, gently descend towards the West, yet neverthelesse, in that it is pent up in the Bosphorus, it floweth with great violence between Scilla and Caribdis, and maketh a great agitation. Like to which, and much greater, is said to be betwixt Africa and the great Isle of St. Lorenzo, where the Waters of the two vast Seas, Indian and Ethiopick, that lie round it, must needs be straightned into a lesse Channel between the said Isle and the Ethiopian Coast. And the Currents must needs be very great in the Straights of Magellanes, which joyne together the vast Oceans of Ethiopia, and Del Zur, called also the Pacifick Sea.

It follows now, in the sixth place, that to render a reason of some more abstruse and incredible accidents, which are observed upon this occasion, we make a considerable reflection upon the two principal causes of ebbings and flowings, afterwards compounding and mixing them together. The first and simplest