i04 PHILOSOPHICAL TRANSACTIONS. [aNNO 1666. 



the tides are out do lie in a manner quite dry ; and may therefore very well 

 be supposed to participate the effect of the menstrual tides many days after the 

 cause of them happens in the open sea ; upon a like ground as in straits and 

 narrow channels, the diurnal tides happen some hours later than in the ocean. 

 And a like account must be given of particular accidents in other places, from 

 the particular situation of those places, as bays, channels, currents, &c. 



5. To the fifth objection, that the spring tides happen not with us just at 

 the full and change, but two or three days after ; I should with the more con- 

 fidence attempt an answer, were I certain whether it be so in the open seas, 

 or only in our channels. For the answers will not be the same in both cases. 

 If only in our channels, where the tides find a large in-draught, but not in the 

 open seas, we must seek the reason of it from the particular position of these 

 places. But if it be so generally in the wide open seas ; we must then seek a 

 reason of it from the general hypothesis. And till I know the matter of fact, 

 I know not well which to offer at ; lest, whilst I attempt to solve one, I should 

 fall foul of the other. I know that mariners use to speak of spring tides at the 

 new and full of the moon ; though I have still had a suspicion that it might be 

 some days after, as well in the open seas as in our narrower channels ; of 

 which suspicion you will find some intimations even in my first papers : but 

 this, though I can admit, yet, because I was not sure of it, I durst not build 

 upon it. The truth is, the flux and reflux of water in a vessel by reason of the 

 jogging of it, though it follow thereupon, yet is for the most part discernible 

 some time after. For there must upon that jog be some time for motion, be- 

 fore the accumulation can have made a tide. And so I do not know but that 

 we must allow it in all the periods. For as the menstrual high tide is not till 

 some days after the full and change ; so is the diurnal high water about as 

 many hours after the moon's coming to south ; I mean at sea, for in channels 

 it varies to all hours, according as they are nearer or further from the open sea : 

 and the annual high tides of November and February somewhat later than 

 (what I conjecture to be from the same causes) the greatest inequalities of the 

 natural days happening in January and October. But this though I can admit, 

 yet (till I am sure of the matter of fact) I do not build upon. And since it has 

 hitherto been the custom to speak with that laxness of expression, assigning 

 the times of new moon, full moon, and quadratures, with the moon's coming 

 to south, for what is near those times ; I did not think myself obliged in my 

 conjectural hypothesis, to speak more nicely. If the hypothesis for the main 

 of it be found rational, the niceties of it are to be adjusted in time from par- 

 ticular observation. 



Having thus given you some answers to the objections you signify to have 



