Page:Philosophical Transactions - Volume 003.djvu/193



8. The usual number of Tydes from New Moon to New Moon, or from the Full to the Full, is Fifty nine.

9. In the River of Severn. 20. miles above Bristol near Newnham, 160. miles from the Rivers mouth (Lundy,) the head of the Floud, at its coming in in Spring-tydes, ariseth in height, like a Wall near nine foot high, and so runs for many miles together, covering at once all the Shoales, which were dry before; at which time all Vessels, that lye in the way of the said Head-tydes, or (as it is vulgarly called) Boar, are commonly overset or carried upon the Banks, and the head of the Tyde being past, such Vessels are left dry again. It flows there but two hours, and eighteen foot in height, and it ebbs ten hours. The reason of the said Boar is doubtless the straightening and shoaling of the River in that place, it being there but half a mile broad; as it is but 20. pearches over, three miles higher; running tapering to Glocester.

So far this Observer; To whom as there are due particular acknowledgements for his care of observing hitherto, and for his frankness of communicating, so he is further desir'd to continue his Observations with as much exactness as may he, according to the directions set, down in the above mentioned Numb. 18. especially to rake particular notice, whether the Annual High-tydes, which he seems to fix on those (be it at New or Full) which happen nearest the Equinox, (be it before or after it) be not always before the Vernal Æquinox in March, and upon the New Moon; and always after the Autumnal in September, and upon the Ful-moon Spring-tydes: For as much as by a former relation, imparted by a curious Gentleman, we have been informed, that the Annual highest Tydes about Chepstow-bridge, were at St. Davids and Michaelmas-Stream, that is, the one a little before the Vernal, and the other somewhat after the Autumnal Æquinox, which agrees also with the Conjecture of at very intelligent Mathematician, who is withal of opinion, that because both are not fat from the Æquinoxes, ( though the one Rh