Page:Walker (1888) The Severn Tunnel.djvu/161

92 return to the face within a minute from the time the shots were fired.

When the works were about half completed, I was persuaded to try compressed lime-cartridges, with which it was stated good work was being done in the coal-mines.

A number of these cartridges were brought down and tried in various places, but with no favourable result.

Generally in ground so hard as that we had to deal with, the lime only blew out its own tamping, and displaced no rock. The experiment, too, was attended with an unfortunate accident. The cartridges of compressed lime are placed in a large bore-hole, drilled to receive them, and a tube, instead of a fuse, is placed in the hole above the cartridges, and when the tamping has been placed, water is forced by a force-pump through the tube on to the cartridges. The swelling of the lime and the generation of gas is to displace the rock.

When one of the holes had just been loaded, my principal foreman, Joseph Talbot, was standing opposite to the hole, and the first of the water had just been pumped in, when the tamping blew out and a quantity of lime was forced into his eyes, and for a day or two it was feared he would lose his sight. Fortunately he entirely recovered; but the short experience was quite enough to convince us that we could make no use of the lime-cartridge system.