§0 PHILOSOPHICAL TRANSACTIONS. [aNNO 1666. 



The sea's ebbing and flowing has so great a connexion with the moon's mo- 

 tion, that in a manner all philosophers have attributed much of its cause to the 

 moon, which either by some occult quality, or particular influence which it 

 has on moist bodies, or by some magnetic virtue, drawing the water towards 

 it,* which should therefore make the water highest where the moon is vertical, 

 or by its gravity and pressure downwards upon the terraqueous globe, which 

 should make it lowest, where the moon is vertical, or by whatever other means, 

 has so great an influence on, or at least connexion with, the sea's flux and re- 

 flux, that it would seem very unreasonable to separate the consideration of the 

 moon's motion from that of the sea: the periods of tides, to say nothing of the 

 greatness of them near the new and full moon, so constantly waiting on the 

 moon's motion, that it may be well presumed, that either the one is governed 

 by the other, or at least both by some common cause. 



But the first that I know who took in the consideration of the earth's mo- 

 tion, diurnal and annual, was Galilaeo, who, in his System of the World, has a 

 particular discourse on this subject; which, from the first time I read it, seemed 

 to me so very rational, that I could never be of other opinion, than that the 

 true account of this great phenomenon was to be referred to the earth's motion 

 as the principal cause of it ; yet that of the moon not to be excluded as to the 

 determining the periods of tides, and other circumstances concerning them. 

 And though it be manifest enough, that Galilaeo, as to some particulars, was 

 mistaken in the account which he there gives of it; yet that may be very well 

 allowed, without any blemish to so deserving a person, or prejudice to the main 

 hypothesis : for that discourse is to be looked upon only as an Essay of the ge- 

 neral hypothesis; which as to particulars was to be afterwards adjusted, from a 

 good General History of Tides ; which it is manifest enough that he had not, 

 and which is in a great measure yet wanting. 



And what I say of Galilaeo, I must in like manner desire to be understood of 

 what I am now ready to say to you. For I do not profess to be so well skilled 

 in the history of tides, as to undertake presently to accommodate my general 

 hypothesis to particular cases; or indeed to undertake for the certainty of it, 

 but only as an essay propose it to further consideration, to stand or fall, as it 

 shall be found to answer matter of fact. 



I consider therefore, that in the tides, or the flux and reflux of the sea, be- 

 sides extraordinary extravagances, or irregularities, whence great inundations or 

 strangely high tides follow, (which yet perhaps may prove not to be so merely 



* It is curious to observe here how near the conjectures of Wallis approached to the true cause and 

 theory of the tides^ afterwards more fully developed and demonstrated by Newton. 



