638 PHILOSOPHICAL TRANSACTIONS. - [aNNO 1701. 



tlie StoLire in Kent, to have been both asstuaries of the northern tide, before 

 the rupture of that isthmus between Dover and Calais ; and the like of the 

 river near Maiden, and other small creeks on the coast, though not so large as 

 those of the Huinber and the Thames, which were then sestuaries of the same sea, 

 as are many others on the coast of Scotland. I say, before that rupture ; for, 

 since that rupture, the case as to the Thames is somewhat altered ; for the 

 western tide between us and France, which was then stopped at this isthmus, 

 now flows on througli that fretum, beyond the mouth of the Thames, as high 

 as the Dogger- sands ; which therefore supplies the aestuary of the Thames, 

 which was formerly furnished from the northern sea. And these smaller aestu- 

 aries might sooner be choaked up by what every tide lodges there, while those 

 larger sestuaries are only shortened and become narrower than they had formerly 

 been. And as to the Thames in particular it seems very evident, if we consider 

 their situation, and the nature of their soil, that much of the low grounds in 

 Kent and Essex, on both sides of the mouth of the Thames, adjacent to the 

 sea, had formerly been sea, as well as that of Romney-marsh. And when the 

 mouth of the Thames was so much wider, no doubt but it flowed much farther 

 than it now does. 



It may perhaps be objected, that the small rivers still remaining in the bottom 

 of these vallies, which may have been supposed to have been sestuaries in former 

 times, run now with more turnings and windings than these vallies themselves 

 do. But this need not at all seem strange, when we may daily see the same in 

 the bottom of a muddy ditch, or water course, when the water is almost 

 drained of^', the mud still remaining soft, that the little water which is left will 

 work out for itself, amidst the mud, a winding passage, according as the mud 

 will more or less give way, much more crooked than the ditch itself when full 

 of water. And the like must needs happen in the gradual draining of such 

 sestuaries, according as the soft earth will permit. Which crookedness will 

 continue when the banks on both sides by degrees grow firmer. 



As to what I observed concerning the Isle of Oxney ; that a low level in that 

 isle, which had for several years lain under water, is now raised by introducing 

 the tide to a considerable height above what it was formerly, and that the chan- 

 nel from thence to Rye is, by the tides passing in and out, become much wider 

 and dee[)er than heretofore. If we look in the more ancient maps of Kent 

 before the year 1 640, we shall find that, what we call the Isle of Oxney, was 

 then only a peninsula, being, by a small isthmus at the north-east corner of it, 

 continued to the rest of the country ; and the tide from Rye to that place, 

 which now flows straight on by the north side of the isle, was there stopped 

 by that isthmus, and wheeled about on the south side of it, or rather, the river 



