Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/449

 stituted in other points of the Quadrant AI, drawing the Tangents in the said points, and the perpendiculars upon the same falling from the terms of the diameters of the Equinoctial drawn from the errect planes by the said Tangents to the plane of the grand Orb; the parts of the said Tangents (which shall continually be lesser towards the Equinoctials, and greater towards the Solstices) shall give us the quantities of the additions and substractions. How much in the next place the least additions differ from the greatest, is easie to be known, because there is the same difference betwixt them, as between the whole Axis or Diameter of the Sphere, and the part thereof that lyeth between the Polar-Circles; the which is less than the whole diameter by very near a twelfth part, supposing yet that we speak of the additions and substractions made in the Equinoctial; but in the other Parallels they are lesser, according as their diameters do diminish.

This is all that I have to say upon this Argument, and all perhaps that can fall under the comprehension of our knowledge, which, as you well know, may not entertain any conclusions, save onely those that are firm and constant, such as are the three kinds of Periods of the ebbings and flowings; for that they depend on causes that are invariable, simple, and eternal. But because that secondary and particular causes, able to make many alterations, intermix with these that are the primary and universal; and these secondary causes being part of them inconstant, and not to be observed; as for example, The alteration of Winds, and part (though terminate and fixed) unobserved for their multiplicity, as are the lengths of the Straights, their various inclinations towards this or that part, the so many and so different depths of the Waters, who shall be able, unless after very long observations, and very certain relations, to frame so expeditious Histories thereof, as that they may serve for Hypotheses, and certain suppositions to such as will by their combinations give adequate reasons of all the appearances, and as I may say, Anomalie, and particular irregularities that may be discovered in the motions of the Waters? I will content my self with advertising you, that the accidental causes are in nature, and are able to produce many alterations; for the more minute observations, I remit them to be made by those that frequent several Seas: and onely by way of a conclusion to this our conference, I will propose to be considered, how that the precise times of the fluxes and refluxes do not onely happen to be altered by the length of Straights, and by the difference of depths; but I believe that a notable alteration may also proceed from the comparing together of sundry tarctstracts [sic] of Sea, different in greatness; and in position, or, if you will, inclination; which difference happeneth exactly here in the Adriatick