cate the position of the strata of various rocks—of the 
same rocks which compose the hills on either side: so, 
for example, the district A between the dotted lines is 
assumed to be that of the upper or white chalk; B, the 
lower or grey chalk; c, to be the place of a series of 
strata, such as the upper green sand; the gault, the 
Folkestone, Sandgate, and Hythe beds; Atterfield clay, 
&c., ec, 
The only question that presents itself to our mind is, | 
whether this chart be correct ; whether the geological lines 
there indicated are the result of test and observation, or 
whether those lines are based on the theory of the 
engineers, that the strata of the hills on either side of 
the Channel pass “ undisturbed” in plane surfaces across 
the Channel, assuming that the strata which formerly 
NATURE 
[| Fan. 20, 1870 
of the Channel. If this be so, it would not be necessary 
to divert the tunnel as indicated on the plan, Nothing 
short of an actual test across the Channel on the line 
selected for a tunnel could, however, settle the question of 
stratification, and determine at what depth a special kind 
of rock, suitable for tunnelling, would be met with. 
The operation of driving the tunnel would have to be 
_ carried on many hundred feet below the mean level of the 
Channel, and, apart from other difficulties attending the 
execution of such an immense tunnel, for which we have 
no precedent eyen on a small scale—the first question 
would be, whether it may be reasonably expected that 
tunnelling would be practicable under such circumstances 
| without meeting with an insurmountable influx of water. 
That we should meet with many fissures and cracks 
PROPOSED RAILWAY TUNNEL UNDER THE CHANNEL. 
s s 
fark ie ee rey SS, 
CJ 1 2 3 o cS co 7 a 
A, upper or white chalk. B, lower or grey chalk. C, upper green sand, gault, Folkestone, Sandgate, and Hythe beds. 
Geological Line, 
Ten Fathom Line . 
D, region 
probably occupied by the Hastings sands. E, Neocomian sand. F, Portland stone and sand. G, Kimmeridge clay, H, Weald 
clay. SS, Borings. 
occupied the Channel were cut away or carried off ; and | 
whether the lines indicated on the map may not princi- 
pally have been produced by constructing the intersec- 
tions of those inclined surfaces with the present bottom 
of the Channel. We fear the geological lines of the 
diagram were mainly obtained on the above theory of 
the engineers, and will therefore in a great measure be 
imaginary. 
It is probable that the strata which form the hills on 
either side will also form the bottom of the Channel, at a 
different elevation ; but it would be rash to say how much 
the difference might be. It will probably vary across the 
Channel, the thickness of the strata remaining nearly the 
same; so it may be presumed that chalk will be found 
within the Dover Straits at certain depths below the bed 
is a matter of course, for it would be difficult to select on 
a rocky surface a few square yards without indications of 
fissures. That water will find its way along cracks we 
know from experience, and as in this instance no water- 
tight strata intervene between the sea and the rocky 
material through which it is proposed to drive the tunnel, 
so, consequently, we must expect that the work of driving, 
the driftways and the tunnel would be “wet.” Although 
the work may be very wet, it will still remain a question 
of quantity, and not only one of quality; and, accord- 
ingly, we must ascertain whether the quantity of water 
that might find its way into the workings would be un- 
manageably large. 
On this point a great deal of misconception may be 
found in “professional” papers. It is asserted, that the 
