Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/422

 but the part C at the same time is retarded in its motion, as being deprived of the progression dependant on the diurnal motion: If we suppose, I say, a tract of Sea as long as the arch B C, we have already seen, that its extreams shall move in the same time with great inequality. And extreamly different would the velocities of a tract of Sea be that is in length a semicircle, and placed in the position B C D, in regard that the extream B would be in a most accelerate motion, and the other D, in a most slow one; and the intermediate parts towards C, would be in a moderate motion. And according as the said tracts of Sea shall be shorter, they shall lesse participate of this extravagant accident, of being in some hours of the day with their parts diversly affected by velocity and tardity of motion. So that, if, as in the first case, we see by experience that the acceleration and retardation, though equally imparted to all the parts of the conteining Vessel, is the cause that the water contained fluctuates too and again, what may we think would happen in a Vessel so admirably disposed, that retardation and acceleration of motion is very unequally contributed to its parts? Certainly we must needs grant that greater and more wonderful causes of the commotions in the Water ought to be looked for. And though it may seem impossible to some, that in artificial Machines and Vessels we should be able to experiment the effects of such an accident; yet neverthelesse it is not absolutely impossible to be done; and I have by me the model of an Engine, in which the effect of these admirable commixtions of motions may be particularly observed. But as to what concerns our present purpose, that which you may have hitherto comprehended with your imagination may suffice.

I for my own particular very well conceive that this admirable accident ought necessarily to evene in the Straights of Seas, and especially in those that distend themselves for a great length from West to East; namely according to the course of the motions of the Terrestrial Globe; and as it is in a certain manner unthought of, and without a president among the motions possible to be made by us, so it is not hard for me to believe, that effects may be derived from the same, which are not to be imitated by our artificial experiments.

These things being declared, it is time that we proceed to examine the particular accidents, which, together with their diversities, are observed by experience in the ebbing and flowing of the waters. And first we need not think it hard to guesse whence it happeneth, that in Lakes, Pooles, and also in the lesser Seas there is no notable flux and reflux; the which hath two very solid reasons. The one is, that by reason of the short-