Page:Philosophical Transactions - Volume 003.djvu/191

 Libra, of the next Tyde after, according as the Moon is near her Full or Change, when the Sun thus enters into the said Signes: And then it flows in height about 7½ fathoms, or 45. foot; the lowest Neap-tydes flowing in height 27. foot.

2. We observe also, that the lowest Neap makes the highest Spring, if the North-East Winds hinder not by blowing hard, and so keep back the Tydes; as usually they do when they blow: whose contrary winds (South-west) if they blow hard, make here the highest Tydes.

3. Concerning our Diurnal Tydes, we observe, that from about the latter end of March till the latter end of September, they are about 1. foot and 3. inches higher perpendicularly in the Evening than in the Morning, that is, if high water happen after the Sun is past the Meridian, or in the Tydes betwixt Noon and Midnight. But from Michael-mas till our Lady-day we find the contrary, the Day-tydes being in that season higher by 15. inches than the Night tydes, or the Tydes between Midnight and Noon. And this proportion holds in both, after the gradual increase of the Tydes rising from the Neap to the highest Spring, and the like Decrease of their Height till Neap again.

4. As for the higest Menstrual Spring-tyde, that is always the third after the Full Moon or Change-day, if it be not kept back by North-East winds, as it hath been, by my own Observations.

5. I have observed several times, that it flows here on the Change-day, when the Moon is East-South-East the Tyde flowing in for the space of 5. hours, and ebbing 7. hours; so that there is an hour and an half difference from the Old Tables, which say, it flowes but to the Moons being East and West: An Error so great, that by all means it ought to be rectified.

6. There is some difference in reckoning the Tydes by the Moons Bearing on such a point of the Compass on the Full or Change day. Fort-hen about that time only will the Rule hold to be exactly true. But from the Change to the Quarters, and from the Full to the Quarters again in the Neap-Tydes, I have observed, it does not flow here by two points of the Compass so long. But concerning the difference betwixt the New and Rh