King’s Wells at Sheernefs, &c. 17 
‘upply of water might be reduced to the drain, which is con- 
tru€ed to prevent as much as poffible the mixture of fand 
with the water, and is found to anfwer the defired end. This 
fuccefs'arofe from various unexpected circumftances ; but I am 
yet at. a-lofs for the caufe of the frefh water, or whence it 
comes. 
I conceive, that oy is a certain diftance from the fea, upon 
every fandy fhore, to which, the falt-water penetrates, where it 
is forced whilft the tide is at its greateft height ; and that fuch 
water, when fo far preffed into the fands, has an aétion back 
towards the fea again, as the tide falls, and continues to have it 
until another tide makes it revert; this may account for the 
filtration of falt-water a certain way into a country; and that 
further, from probably higher Jurfaces, there may be frefh-water 
in the fame continuation of fands, and the feparation difco- 
verable to a degree of great accuracy; whether this a¢tion of 
falt-water in the fand, by friGtion, can render it frefh, or of a 
lefs degree of falt, I will not pretend to judge. I prefume the 
contrary ; but am even under that idea at a lofs: to know how 
fo much frefh water gets into the fand at Landguard-Fort, it 
being fo entirely feparated from the {pring of the country. It 
is evident, upon a full confideration of the fubjeét, that the 
fea, to the height of Jow water; will penetrate a vaft diftance 
into a fandy country, by filtration; and to that height on/y, it 
having fo fara conftant preffure, and no reraction; the water, 
therefore, being once in the fand, can never return by the fame 
paflage, the caufe of its entrance ftill remaining; whereasin 
the higher furfaces, the rife'and fall of tides muft keep it in 
conftant movement, and the diftance of filtration will bear a 
proportion to the duration of preffure which gave it original 
motion. It is probably not fo eafy to account for a body of 
Vor. LXXIy. 1G BD _. -fxefhe 
