1878.] 285 
(Chevalier, 
sufficiently acquainted with the geology and hydrography of the Channel. 
The co-laborers of Mr. Lavalley, in 1876, were Mr. Larousse, late hydro- 
graphical engineer of the National Marine Corps, and Messrs. Potier and 
DeLapparent, engineers in the National Corps of Mines. All three by their 
zeal, their intelligence, and their devotion to a difficult task the national 
importance of which they fully appreciated, have entitled themselves to 
the consideration of the learned world, and to your gratitude. 
We propose to give you in some detail the principal results of the three 
classes of operations above mentioned, and to this end it is only necessary 
to sum up the reports which have been addressed to you. These reports, 
let me add, are eminently worthy of your attention, and if you will read 
them in extenso you cannot but approve of them. 
I. The study of the two coasts. The study of the shores of the Channel 
proves that the geological formation is very much the same throughout 
that part which particularly concerns us, comprising the chalk formation. 
The same layers are found on the two coasts, of the same character, and 
what is remarkable, having the same thickness. Hence, the presumption, 
corroborated by other circumstances, that formerly in a prehistoric age, in- 
stead of an arm of the sea separating the two shores, there existed a con- 
tinuous surface of ground, more or less undulated, between the points 
where since have arisen the towns of Calais and Boulogne on the one 
side, and Folkestone and Dover on the other. The Channel, in such a hy- 
pothesis, would be due to the continual erosion of a soil of little consis- 
tency, as is usually the case with the chalk formation, this soil having 
yielded by degrees to the shocks of the waves of the Northern Ocean ever 
violently agitated during the stormy season. From this circumstance we 
derive the hope that the strata to be met with beneath the sea, and through 
which the tunnel would pass would be as a general thing continuous, and 
present, if any thing, deflections merely, to which the track of the subter- 
ranean railway might conform without much inconvenience. 
This hope is substantiated by the fact that on both sides of the Channel 
the layers of clay forced from the horizontal position in which they must 
originally have lain, have not been very much displaced. Throughout 
the greater extent of the Channel on the French side it is a seventh 
merely, a fact which would appear to indicate that the subterranean com- 
motions which caused the deviations in the layers from the horizontal plane 
were not of much moment. 
II. Geological chart of the bed of the Channel. This portion of the 
studies pursued is worthy of increased attention. At first sight it seemed 
an insoluble problem, for in almost every region of the earth the bottom of 
the sea consists of sand and gravel, covering to a great or even remarkable 
depth the massive rocks that cling to the solid body of the planet. In the 
Channel of the Straits of Calais, however, runs a current at the rate of 
about two or three knots an hour, which sweeps away the sand and gravel 
as it is deposited, and does it the more effectually, from the circumstance 
of its being quite narrow, and of a depth of not more than 30, 40, or 50 (53 
