520 PHILOSOPHICAL TRANSACTIONS. [aNNO 1 67O. 



because, if the moon be in perigaeo at this spring tide, she will be in apogaeo at 

 the next. 



But I conceive the best touchstone to prove the soundness of my opinion 

 is, to have it observed, whether those neap-tides be not apparently higher 

 that happen at the moon's being in perigaeo either at the first or last quarter : 

 because it is a received and demonstrable truth in astronomy, that the moon 

 being in perigaso at either quarter, comes then nearer the earth than when it is 

 in perigaeo at the change or full. And I could wish, for the further clearing of 

 this matter, that observation were made at Bristol (because there is the most 

 considerable flux and reflux of any port of England,) whether this year, 1670, 

 the tides be not higher when the ]) passes ^ , 7", and y , than when she 

 passes through the opposite signs Tl^, £i and TT[ ; and particularly whether the 

 spring tides be not sensibly higher after the change than after the full in 

 February, March and April ; and higher after the full than after the change in 

 August, September, and October ; and also, whether the neap tides in May 

 and June rise not apparently higher than expected. I am promised the ob- 

 servation shall be made here at Weymouth for this whole year round ; from 

 whence I have already received this account, that this present Februar)^ 

 1669-70, the spring-tides ran very high after the change, though the weather 

 was pretty calm, and that wind that was not very favourable to the tides, and 

 that the spring-tides after the full were very low, and weak ; which is exactly 

 according to my conjecture. 



Dr. JFallis's Answer to the foregoing Ajiimadversions^ extracted from 

 Us Letter of March 19, l66'9-70. N' 64, p. 2068. 



That the winds have a great influence on the tides of particular coasts and 

 havens, according as they are more or less stiff" or slack, and blow from this or 

 that part, I do not at all question ; but took for granted, as generally received, 

 and upon good grounds. And the like I say of land waters ; which are, as to 

 inland rivers, very considerable : especially as to inundations upon rising of the 

 water : which is rather by checking than promoting the tides. But he need 

 not wonder, that in my essay, though I grant both these, I said so little of 

 either, because it was wholly beside my business ; which was to give a stati- 

 cal account of stated periods (diurnal, menstrual, and annual,) arising from 

 regular motions ; not of accidental extravagances, such as these are ; and 

 therefore I did, in the beginning of that discourse, preclude the consideration of 

 the advantage or disadvantage which should arise from such uncertain con- 

 tingences, as extrinsical to that business. 



