The answer is this—He had been informed by geologists that quicksand prevailed lower down, and the shaft that he sank for drainage below the level of the proposed tunnel, indicated that this view might be correct. In fact, when he got down 80 feet, the soil gave way, and water and sand rushed upwards. He was therefore apparently between the Thames and the quicksand. The Tower Subway, constructed in 1869, and driven through the solid London clay, is, however, 60 feet deep where it commences at Tower Hill.
Work went steadily forward at Brunel’s tunnel until the 18th of May. Mr. Beamish, the assistant engineer, was in the cutting on that day, and as the tide rose he observed the water increase about the shield; clay showed itself and gravel appeared. He had the clay closed up, and went to encourage the pumpers. Suddenly, before he could get into the cells, a great rush of sludge and water drove the men out of the cells, extinguished the lights, floated the cement casks and boxes, and poured forward and ever forward, filling the tunnel with the roaring of the flood.
The Thames had broken in with a vengeance this time, and drowned the tunnel.
CHAPTER II.
UNDER THE RIVER.
Happily no one lost his life.
The men retreated before the advancing wave, and as they went they met Brunel. But the great engineer could do nothing just then, except, like them, to retreat. The lights yet remaining flashed on the roaring water, and then suddenly went out in darkness.
The foot of the staircase was reached, and it was found thronged with the retreating workers. Higher and higher grew the surging flood; Brunel ordered great speed; and scarcely were the men’s feet off the lower stair when it was torn away.
On gaining the top, cries were heard; some calling for a rope, others for a boat. Some one was below in the water! Brunel himself slipped down an iron rod, another followed, and each fastening a rope to the body of a man they found in the flood, he was soon drawn out of danger. On calling the roll, every worker answered to his name. No life was lost.
So far, good; but what was to be done now? The tunnel was full of water. To pump it dry was impossible, for the tide poured in from the Thames.