THE CHANNEL TUNNEL. 
395 
Mathieu. About the year 1800 he drew up plans, which were 
for a while exhibited in Paris, but which have long since been 
lost. In 1853 Mr. W. Austin devoted some attention to this 
subject, and published his plans in 1856, proposing to construct 
a tunnel from Boulogne to Cape Grisnez. Nearly the same line 
was chosen by M. Thome de Gramond, who, in 1857, published 
an elaborate work on the subject. Since that time the 66 Channel 
Tunnel,” in one form or other, has been pretty constantly before 
the public. Mr. W. Low had also devoted much attention to 
this question, and he concluded that the only mode of making 
a tunnel would be by taking it through the Lower Chalk. 
With this proposal M. de Gramond subsequently agreed, and he 
has now abandoned his original scheme in favour of that of the 
English engineers. To Sir J. Hawkshaw (the President Elect of 
the British Association) is due the credit of fully working out 
and developing the plan of carrying a tunnel through the Chalk. 
At his request Mr. E. C. H. Lay, in 1864-5, made a detailed 
geological examination of the coasts, and constructed maps and 
sections of the strata. Sir J. Hawkshaw, with others, subse- 
quently employed a steamer to take soundings in the Channel 
along or near to the line of the proposed tunnel, and he also 
made deep borings through the Chalk on each coast. The results 
of all these investigations are accessible, and we therefore pos- 
sess a good deal of information bearing upon the question. 
For several years it seems to have been generally conceded 
that the plan with which the names of Sir J. Hawkshaw and 
Mr. Brunlees are associated — that of taking a tunnel through 
the Chalk — is the most feasible, and comparatively little atten- 
tion has been paid to other propositions. In December 1873 
Prof. J. Prestwich read a very interesting paper before the In- 
stitution of Civil Engineers, in which he carefully examined the 
geological questions connected with the various schemes ; and, 
disagreeing to some extent with all, he proposed to construct a 
tunnel through the Palseozoic rocks which underlie the secondary 
strata of the south-east of England, and which come to the surface 
near Marquise, in the Boulonnais. A long discussion took place 
after the reading of the paper, in the course of which much 
information was elicited regarding points connected with the 
tunnel.* 
In considering the suitability of certain strata for sub-aqueous 
tunnelling, there are three main points to be considered. We 
should select strata which are (1) impervious , (2) continuous , 
and (3) sufficiently thick. Perhaps the only beds which fulfil 
all these conditions are the London Clay and the Kimeridge 
Clay ; but any tunnel to pass wholly through either of these for- 
mations must be very long. Permeability and impermeability 
* See the full report in u Proc. Inst. Civ. Eng.,” vol. xxxvii., p. 110. 
