1875.] The Channel Tunnel. 503 
an inclination of one foot in 80 to the junction with the 
drainage driftway, and then at a gradient of one to 2640 
to the centre of the Straits, where the tunnel from the Eng- 
lish shore will meet that driven exactly in the same manner 
from the French shore, and, being united with it, will com- 
plete the submarine railway under the Channel. The 
drainage will be from the centre of the tunnel to either 
end. . 
In the execution of this work a driftway, g feet in 
diameter, will first be: carried right through, and this 
will afterwards be enlarged to the full size of the tunnel. 
The problem of the execution of the tunnel in a reasonable 
time has been simplified by the invention of tunnelling 
machinery, and the machine of Mr. Dickenson Brunton, 
which has been tried on a practical scale by the company 
in the lower or grey chalk, has been quite successful. The 
machine works like an augur boring a hole in wood. The 
chalk is cut off in slices, which break up and fall upon an 
endless band, which loads them into wagons behind the 
machine. The apparatus was tried by the Company at 
Messrs. Lee’s Cement Works, Snodland, near Rochester, in 
the grey or lower bed of chalk, such as underlies the 
Channel. It made a driftway of 7 feet diameter, and it 
advanced at the rate of from a yard to a yard and a quarter 
per hour. At this rate it would only require two years to 
drive a driftway of 7 or g feet diameter from one 
side of the Channel to the other, a machine being started 
from each side. The cost of driving a heading would con- 
sist—Ist, of tunnelling machines, pumps, and pumping 
engines; 2nd, the hand labour, which would not be con- 
siderable, as the machine requires but few hands to work it; 
and, 3rd, interest on the capital expended during the execu- 
tion of the work, which might last two years or more. 
Taking these three elements of expenditure into considera- 
tion, and according to the calculations of experienced con- 
tractors, it has been found that the driftway could be 
executed for £800,000, if it required only two years to 
make it. 
As soon as the driftway was completed the success of the 
undertaking would be assured. It would furnish the neces- 
sary data for an exact estimation of the cost of the whole 
work and the time necessary for its execution. In fact, 
all that would be necessary would be to enlarge the driftway 
to the dimensions of an ordinary railway tunnel. It has 
been estimated by some engineers and contractors of con- 
siderable experience that after the driftway was finished, 
VOL. V. (N.S.) ; 3s 
