VOL. I.] PHILOSOPHICAL TRANSACTIONS. 113 



gent persons at London or Greenwich, but rather nearer the sea or upon the 

 sea-shore, would make particular observations of all the spring tides, (new moon 

 and full moon) between this and the end of November; and noting the hour 

 and the perpendicular height ; that it may be seen whether those in September 

 or November be highest : And also to observe the low waters ; which may be 

 easily done by a mark made upon any standing post in the water, by any water- 

 man or other intelligent person who dwells by the water side. 



Considerations and Inquiries concerning Tides. By Sir Robert 



Moray. N" 17, p- 298. 



It being observed, that tides increase and decrease regularly at several seasons 

 according to the moon's age, so as about the new and full moon, or within two 

 or three days after, in the western parts of Europe, the tides are at the highest, 

 and about the quarter moons at the lowest, the former being called spring tides 

 the other neap tides ; and that according to the height and excesses of the tides, 

 the ebbs in opposition are answerable to them, the highest tide having the 

 lowest ebb, and the lowest ebb the highest tide ; the tide from the quarter to 

 the highest spring tide increasing in a certain proportion, and from the spring 

 tide to the quarter tide decreasing in like proportion as is supposed ; and also 

 the ebb rising and falling constantly after the same manner : It is wished that 

 it may be inquired, in what proportion these increases and decreases, risings and 

 fallings, happen to be in regard of one another ? 



And it is supposed, from some observations made by the above-mentioned 

 gentleman, that the increase of the tides is made in the proportion of sines, 

 the first increase exceeding the lowest tide in a small proportion, the next in a 

 greater, the third greater than that ; and so on to the middlemost, where the 

 excess is greatest, diminishing again from that to the highest spring tide ; so as 

 the proportions before and after the middle do greatly answer one another, or 

 seem to do so. And likewise from the highest spring tide to the lowest neap 

 tide, the decreases seem to keep the like proportions ; the ebbs rising and fall- 

 ing in like manner and in like proportions. All which is supposed to take place 

 when no wind or other accident causes an alteration. 



And as it is observed, that upon the main sea-shore the current of the ebbings 

 and fiowings is sometimes swifter and sometimes slacker than at others, so as in 

 the beginning of the flood the tide moves faster but in a small degree, in- 

 creasing its swiftness constantly till towards the middle of the flood, and then ' 

 decreasing in velocity again from the middle to the top of high water; it is sup- 

 posed that in equal spaces of time, the increase and decrease of velocity, and 



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