216 Geology of the Straits of Dover. [April, 
would come on; but where the outcrop may be, or what 
the thickness of the various beds, we do not know.* 
A similar doubt hangs over the submarine range of the 
Lower Greensand divisions, other than the Folkestone 
Beds. We have seen that the clayey Sandgate Beds and 
the calcareous Hythe Beds are well developed, and have 
their normal characters, on the Kentish coast; whilst on the 
French coast they are wholly absent. Somewhere, then, 
in the bed of the Channel these also must disappear; but 
where this change takes place we cannot tell. 
There are two principal schemes proposed for connecting 
England and France by a submarine tunnel. ‘There is 
that with which the names of Low and Hawkshaw are 
associated, which is proposed to run from near the South 
Foreland to a point between Sangatte and Calais. This 
tunnel it is supposed will be made wholly through the 
Chalk. The other is that of M. Thomé de Gamond, which 
he proposes to take from Eastwear Bay, near Folkestone, to 
Cap Grisnez.t This would pass through a number of 
different beds; how many we cannot tell, for it crosses the 
lines along which the changes above indicated must: some- 
where occur. There is no doubt that it would pass through 
all the English divisions of the Lower Greensand, for these 
it would intersect very near the coast; and we cannot 
suppose that the change which these must undergo takes 
place suddenly. Farther out in the Channel it would 
probably go through Weald Clay, possibly it might touch 
the Hastings Beds, beyond this it might intersect the 
Portland, and, finally, it would cut through the Kimeridge. 
But as we have no certain knowledge, nor even probable 
conjecture, where the outcrops of these various divisions 
occur, we cannot tell where the tunnel would intersect 
them. The various beds intersected by this tunnel are of 
very different characters ; some are highly porous, some are 
wholly impervious. They all crop up somewhere in the bed 
of the Channel, and the porous strata among them are no 
doubt fully charged with water. There are two tunnels on 
the South Eastern Railway which pass through the Lower 
Greensand. There is that on the main line to Dover at 
Saltwood, which is driven partly through the porous 
Folkestone Beds and partly through the underlying Sand- 
* M. Thomé de Gamond dived to the bottom between the Varne and the 
English shore, and brought up specimens of ‘‘ Weald Clay;” but the exact 
spots at which they were obtained is not stated. 
+ M. de Gamond has apparently given in his adhesion to the schemes of 
Messrs. Low and Hawkshaw, so that there is really only one proposal now 
before the public. 
