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A LETTER
SIR, In my Hypothesis for Tydes, you may remember, that I cast the Annual High-Tydes not on the Two Æquinoxes, about the 11. of March and September; nor yet on the Apogæum and Pegæum of the Sun, about the middle of June and December; but (as proceeding from a Complication of those two Causes) on a Midle time between the Perigæum and the two Æquinoxes, (like as is the greatest Inequality of the Natural daies, proceeding from a Complication of the same Causes.) And particularly, for the Coast of Kent (and consequently the Rivers of Thames and Medway) about the beginning of November and February: which agrees with Observations on those Coasts, and particularly with that of yours of Febr. 5. this year.
The last year, when I was present in the R. Society, I remember, an account was brought us of the Annual High-Tydes on the Severn, and at Chepstow-bridge, to be about the beginning of March, and the end of September. Which though they agree not with the particular times on the coast of Kent, yet in the general they agree thus far, That the one is about as much before the one Æquinox, as the other is after the other Æquinox. You now acquaint me with High-Tides about February 22. about the coast of Plimouth, which is later than that of the coast of Kent, but sooner than that on the Severn. And I doubt not but in other parts of the world will be found other Varieties.
The reasons of these Varieties are (as I have formerly signified) to be attributed to the particular Position of those parts, rather than to the general Hypothesis. Of which this, in brief, may serve for some account at present. The General Hypothesis of the Earths diurnal Motion from West to East, would cast that of the Waters, not following so fast, from East to West; which causeth the constant Current within the Tropicks, where the Circles are greatest, west-ward from the Coast of
Africa
