Safety lamp, Ashworth no.4, Clanny type (bonnetted), from the Royal Commission on Accidents in Mines 1879-86, maker: J. Davis and Son, Derby, marking: makers name, 1884

Presented by The Royal Commission on Accidents in Mines.

The chief feature of this lamp is the double bonnet. Air enters both vertically and horizontally on the flange above the glass, and has to pass two rows of holes in the inner bonnet before passing the gauze. The top of the inner bonnet is a truncated cone, so as to retard the exit of the waste products. A screw lock is fitted. Weight, 2.87 lb. This lamp resisted an explosive mixture whose velocity was 2,800 ft. per min. Mr. J. Ashworth in 1887 patented a modification of this lamp, as a Mueseler, which rendered it safe at still higher velocities, but the circulation being so devious made it difficult to light.