5l6 PHILOSOPHICAL TRANSACTIONS. | ANNO I67O. 



Extract of a Letter from Mr. Joseph Childrev to the Right Rev. 

 Seth, Lord Bishop of Sarum ; containing some Animadversions of 

 the Rev. Dr. John Wallis's Hypothesis about the Flux and Reflux 

 of the Sea, published in N" 16 of these Tracts. N" 64, p. 2061. 



My intention is not to argue against that part of the hypothesis, that relates 

 to the common centre of gravity of the earth and moon, and the diurnal and 

 menstrual vicissitudes of the tides, the author's discourse being, in myjudg- 

 ment, so rational and satisfactory as to those, that I cannot see what clear ob- 

 jection can be made against it. But that which I would beg his leave to except 

 against, till better reason convince me, is his opinion concerning the annual 

 vicissitudes, and the true cause thereof, which he supposes to be quite another 

 thing from the common centre of gravity, namely the inequality of the natural 

 days. For I fear he may be mistaken in the time of the annual vicissitudes, 

 which he contends to be about AUhallondtide and Candlemas : And the reasons 

 of my fear are these ; 



1 . Because, if he dare stand to the general judgment of seamen, he will find 

 very few of our English seamen of that mind, who used to say, either that the 

 time of the year signifies nothing at all, or, if it do, that the highest tides of the 

 year seem to happen rather about the equinoxes, than those two other assigned 

 times, when the natural days are longest and shortest. 



1. Whereas he gives an instance or two of very high tides in the Thames in 

 November l66o and l665; the truth of which we need not question, and of 

 which there are sundry other the like instances in our English chronicles ; I 

 have reason to believe, that those high tides proceeded from another cause 

 than what he supposes. For first. If that which he supposes should be the 

 cause, the like high tides might be expected every November, and they 

 should happen as frequently about February as about November; of which yet 

 he gives not one instance. And though I have perused thoroughly that perfect 

 collection I have of all the high tides in the Thames that our chronicles take 

 notice of since the conquest, I can hardly find one such high tide in the 

 Thames in February, or thereabouts. Secondly, Those high tides in the Thames 

 in November, if we dare credit the London watermen, are caused by the coming 

 down of the land- waters after a very great rain, which being encountered by the 

 tide of the flood from the mouth of the Thames, cannot but swell to an 

 unusual height. Now if the great rains fall so, that the land -waters come down 

 to the flowing part of the Thames, just upon the full or change, when the 

 spring tides happen, as they did (for example) September 30, 1555, and October 



