Py 
1878. | 287 [Chevalier, 
quently in France, where the working of the most productive mines of the 
North and of the Straits of Calais has obliged us to sink numerous shafts 
through the cretaceous formation. The result of a long experience acquired 
by the coal miners is that the upper layers contain what are called the 
niweauc, subterranean sheets of water, the draining of which is very ex- 
pensive. The miners, in sinking the shafts, consider their difficulty at an 
end when once they have reached the lower layers known among them as 
diéves, elsewhere called Rouen chalk. In the greater number of instances, 
these layers have been found to contain very little water, and may there- 
fore be considered practically impermeable. 
It happens at times that among these same layers some that are on a 
higher level are crossed by fissures through which part of the water con- 
tained in the upper beds finds its way. These waters, as they descend, 
meeting the lower and more compact layers of Rouen Chalk, can penetrate 
no further, and accordingly gush forth into the open air wherever they 
find an issue. This it is which gives rise on the French coast to the sources 
of the Cheu d’Escalles, and in England to those of the Lydden Spouts. 
But the volume of water of this description, which would be found in ex- 
cavating the tunnel, would be such as could easily be drained by pumps, 
thanks to the great power which our modern exhausting machines have 
acquired ; and no alarm need be felt on that account. 
It being, therefore, evidently to our interest to place the submarine rail- 
way as much as possible in the déeves or Rouen Chalk, our engineers then 
applied themselves to the task of computing the space which these layers 
occupy in that part of the submarine rock which is accessible to us; as 
also the degree of regularity which they present. 
The result of their labors affords good ground for the belief that through- 
out the whole width of the channel, except in the neighborhood of the two 
shores, the Rouen Chalk, or lower stratum of the cretaceous formation, is 
of remarkable regularity, so much so, indeed, that it would be possible to 
lay the submarine railway almost in a straight line through it, and at a 
very ordinary depth. At ashort distance from the French coast, where 
the Quenoc rocks are to be seen, and also in proximity to the English 
shore, on the reef of Varne, the upheavals of the earth are found by our 
engineers to have caused a deflection in the layers, but without severing 
them. 
It does not appear that there exists elsewhere throughout the whole 
width of the channel, at least in the part which concerns us, a single break 
which might be considered an essential obstacle. Indeed, the study of 
the layers comprising the Rouen Chalk even suggests the practicability of 
so constructing the tunnel as to enable us to enter this particular formation 
in France, and to reach the open air in England without having ever 
quitted it. 
The only objections which might be brought to bear against this idea 
with regard to the whole length of the line, comprising the approaches 
from the mainland to the sea, would be such as might be drawn, for ex- 
