Page:Walker (1888) The Severn Tunnel.djvu/159

Rh drills made by the Great Western Railway Company at Swindon, from a pattern of their own. This proved to be an excellent drill for making rapid progress; but it was complicated in design, and required constant repairs.

Another drill used was the ‘Darlington,’ which we liked better, because it required so little repairs. One of these drills could work for six months, after being started, without being repaired at all.

In addition to these we had several others, among them the ‘Duncan’ drill, which did excellent work.

Several methods have been tried for holding the drills in working a heading.

I think decidedly the best is the system adopted by the Great Western Company originally, of a heavy casting, called, from its shape, a ‘harp,’ with sliding bars that can be placed at any angle, and each bar carrying drills. These harps were made to run upon a strong frame on flange wheels of the same gauge as the road used for the skip-trolleys.

They could be pushed forward into the face, and when the holes were drilled, and before they were charged and fired, could be run back a short distance, out of danger from the blasting, and brought forward again when the material brought down by the blasting had been cleared up.

We used all kinds of explosives in the work: dynamite, gelatine, tonite, gun-cotton, compressed powder, and ordinary powder.

Powder made so much smoke as to be very