A NEW PLAN OF TUNNELLING, calculated forg

opening a Roadway under the Thames.

By M. J. BRUNEL, Esa. C.E. F.R.S.

To discover convenient and efficacious means for opening a spacious sub. terraneous communication between the shores of a great river, without oc- casioning any obstruction to the navigation, has long been a desideratum of considerable importance with the public, and in the estimation of scientific engineers. The difficulties which have opposed themselves to every attempt that has hitherto been made to execute a Tunnel under the bed of a river, have been so many and so formidable as to have prevented its successful termination in those instances where the attempts have been made.

To propose therefore the formation of a Tunnel after the abandonment of these several attempts, may appear somewhat presumptuous: on inquir- ing, however, into the causes of failure, it will be found that the chief dif- ficulty, to be overcome, lies in the inefficiency of the means hitherto em- ployed for forming the excavation upon a large scale.

In the case of the drift-way made under the Thames at Rotherhithe, in 1809, the water presented no obstacle for 930 feet; and when a great body of quicksand gave way, and filled the drift, the miners soon overcame this obstruction, and were able to proceed until they were stopped by a second irruption, which, in a few minutes, filled it. Nothing comes more satisfac- torily in support of the system that is adopted here, than the result of the operations that were carried, under that circumstance, to anextent of 1011 feet, and within 130 feet from the opposite shore.

Itis to be remarked that at the second irruption, on examining the bed of the river, a hole was‘discovered 4 feet diameter, 9 feet deep, with the sides perpendicular;—a proof that the body of quicksand was not extensive; but what is most remarkable, is, that this hole could be stopped merely by throwing from above, clay partly in bags and other materials: and after pumping the water out under a head of 25 feet of loose ground and 30 feet of water, the miners resumed the work, and proceeded a little further; but finding the hole at the first irruption increased, and the filling over the second very much sunk, the undertaking was abandoned.