But the Gentleman, to whom the _Island_ belongs at present, and divers of his Brothers and Friends, knowing and discreet persons, and expert in all such parts of Sea-matters, as other _Islanders_ commonly are, though I shrewdly suspected their skill in Tides, when I had not yet seen what they told me, and I have now related of these irregular Courses of the Tides, did most confidently assure me, and so did every body I spake with {55} about it, that there is yet another irregularity in the Tides, which never fails, and is no less extraordinary, than what I have been mentioning: which is, That, whereas between the _Vernal_ and _Autumnal Equinoxes_, that is, for six Moneths together, the Course of irregular Tides about the Quartermoons, is, to run all day, that is, twelve hours, as from about 91/2 to 91/2, 101/4 to 101/4 _&c. Eastward_, and all night, that is, twelve hours more, _Westward_: during the other six Moneths, from the _Autumnal_ to the _Vernal Equinox_, the Current runs all day _Westward_, and all Night _Eastward_. Of this, though I had not the opportunity to be an Eye-witness, as of the other, yet I do not at all doubt, having received so credible Information of it. To penetrate into the _Causes_ of these strange Reciprocations of the Tides, would require exact descriptions of the Situation, Shape, and Extent of every piece of the adjacent Coasts of _Eust_ and _Herris_; the Rocks, Sands, Shelves, Promontorys, Bays, Lakes, Depths, and other Circumstances which I cannot now set down with any certainty, or accurateness; seeing, they are to be found in no _Map_, neither had I any opportunity to survey them; nor do they now occur to my Memory, as they did some years ago, when upon occasion I ventured to make a _Map_ of this whole _Frith_ of _Berneray_, which not having copied, I cannot adventure to beat it out again. * * * * * __Monsieur Auzout_'s Judgment touching the Apertures of _Object-Glasses_, and their _Proportions_, in respect of the several _Lengths_ of _Telescopes_._ This Author, observing in a small _French Tract_ lately written by him to a Countryman of his, Monsieur _L' Abbe Charles_; That great _Optick Glasses_ have almost never as great an _Aperture_ as the small ones, in proportion to what they Magnifie, and that therefore they must be more dim; takes occasion to inform {56} the _Reader_, that he hath found, that the _Apertures_, which _Optick-Glasses_ can bear with distinctness, are in about a _subduplicate proportion_ to their _Lengths_; whereof he tells us he intends to give the reason and demonstration in his _Diopticks_, which he is now writing, and intends to finish, as soon as his Health will permit. In the mean time, he presents the _Reader_ with a _Table_ of such _Apertures_; which is here exhibited to the Consideration of the Ingenious, there being of this _French_ Book but one Copy, that is known, in _England_. A _TABLE_ of the _Apertures_ of _Object-Glasses_.