Notwithstanding these ingenious contrivances for ensuring the progress of the work (which reflect great credit upon the.talents of the engineer), an irruption of water took place on the 18th of May, 1827; and as some account of the cir cumstances attending it may prove of importance to persons engaged in, or about to undertake, similar works, we shall here give it from the pages of a pe riodical journal published at the time.
For several weeks previous to the irruption of the water, it was discovered, by the frequent descent of pieces of bone, brickbats, coals, &c., from the bed of the river to the works, that the earth, or rather the mud between the water and the tunnel, was exceedingly loose, and even at times in motion. Although much water had occasionally penetrated the works, the engine was found sufficient to remove it, and the work proceeded with very little interruption, till that time when the irruption of water between the shield and the brickwork was ao great, as to oblige the men to make a hasty retreat, which they all did in safety. This irruption, which soon filled the tunnel, was much augmented by the action of the water on the last row of brickwork, before it was completed, and the cement had had time to set. On examining the bed of the river, after the acci dent, with the diving-bell, a spacious cavity was discovered over the spot, which terminated in a small hole, descending into the tunnel between the shield and the brickwork, as represented in the annexed sectional sketch. This bole, as well as a second, which subsequently broke out in another part of the cavity, was afterwards filled up with bags of clay, and large quantities of loose clay and gravel, thus making an artificial bed to the river; and this new-made part was protected from the effects of the tide, by a raft thirty-five feet square, skirted with a tarraulin, covering, in all, about 8,800 square feet. After a while, this artificial covering having sufficiently settled, the water was drawn off by the engine, and the workings recommenced : after clearing away all obstructions before the shield, that piece of mechanism was found to be quite uninjured.
This magnificent unctertaking was, however, doomed to a second misfortune, of a more disastrous character, which took place in January 1828, and was attended with the lamentable loss of six lives. "The tide had just began to flow," says Mr
Brunel, jun., " and finding the ground tolerably quiet, we proceeded by begin ing at the top, and had worked about a foot down wards, when, on exposing the next six inches, the ground swelled suddenly, and a large quantity burst through the opening thus made. This was followed instantly by a large body of water. The rush was so violent as to force the man on the spot where the burst took place, out of the frame or cell, on to the timber stage behind the frames." A general retreat instantly took place ; but the agitation of the air, by the rush of water, having extinguished all the lights, confusion ensued; the timber stage was thrown over by the torrent, knocking down under it several men, and the tunnel rapidly filled. Those who could get to the eastern arch effected their escape, while others were carried by the force of the current to the end of the shaft. Of eighteen men, besides Mr. Brunel, jun., who were thus placed at the mercy of the torrent in utter darkness, six were drowned, and the remainder, more or less injured, were taken out of the water for the most part in a state of extreme exhaustion. The foregoing wood cut, which affords a correct represen tation of the lamentable occurrence, is inserted principally on account of its embracing an accurate longitudinal section of the tunnel, and of the mechanism of the movable shield on the left band, through the upper part of wl:ich tLe water found entrance ; thdarched passages delineated in the back-ground, repre sent three of the entrances into the eastern arch, which is a parallel tunnel ; these arched passages are continued at uniform distances throughout the whole length of the work. One of the tunnels was intended for the traffic from the north to the south shore of the Thames, and the other fur the traffic from the south to the north, to prevent interruptions ; a flagged foot-path, as well as a paved carriage road, being made in both the east and west tunnels, as shown in the cross section of the work in the lower part of the preceding cut, which we shall presently explain.