Page:Walker (1888) The Severn Tunnel.djvu/96

Rh , provided in case of such accidents. Before the man could stop the engine it came in again with a thundering blow, and then one of the men who had been watching at the bottom of the pit ran up with terror in his face to say that the great pump had burst near the bottom, and that a piece more than 18 inches across had been driven out of the working-barrel close by him as he stood on the staging. It was useless to work the other pump, so it was stopped, and in a few hours the works at the main shaft were again in the position they had been seven months before—full of water to the level of the tide.

At first no one could understand the cause of this accident; but without wasting time we proceeded again to pull out the 38-inch pump.

The rising-main, being of wrought-iron, was found to be perfect as when it had been lowered; but when we reached the working-barrel, which was of cast-iron, it was found to be split from end to end, and a large piece broken out of the one side, very much as the man had described it. The valve-piece below the working-barrel was also split, and the valve was missing; this latter was found in the suction-piece or wind-bore.

On examination of the pump when pulled out, we found that the bottom valve had had no valve-seat on which to rest, but was let into a taper in the cast-iron valve-piece; the taper being 16 inches long, and only ⅜ ths of an inch larger at the top than at the