WORK OF THE SAFETY IN MINES RESEARCH BOARD 587 
Experiment IV.—Experiment showing the ignition of firedamp by heat of impact 
of handpick on rock. 
The apparatus consists of a wooden box 2 ft. by 1} ft. by x ft., fitted with 
oiled paper releases and a glass observation window. Attached to the pick is 
a rubber diaphragm, covering a circular hole in the cover of the chamber. 
The stretching of the rubber is sufficient to allow of a good blow of the pick. 
Sufficient pure methane is admitted to the chamber to give an approximate 
7 per cent. methane-air mixture. A sampler, fitted with platinum elec- 
trodes, is attached to one side of the chamber to check this percentage. 
The rock used is that suspected of causing ignition at Canavan’s Mine, 
Valleyfield Colliery. A glancing blow of the pick on the rock must be 
delivered to cause ignition, there being a bright yellow flash at the point 
of contact. 
Experiment V.—Experiments on signalling with bare wires. 
Pit conditions render it necessary that signalling should be possible at 
any point in the roadways over a distance of perhaps four miles, and it is, 
therefore, only possible to do this by means of bare wires which are 
crossed to make the signal. 
The bare wire connections from a signalling bell are brought into contact 
in a mixture containing 8-3 per cent. of methane, confined in a glass vessel 
of approximately 400 cc. capacity. A vertical exit tube, closed by a loosely 
fitting rubber bung, provides a release on ignition. 
Bell—A.T.M. (Automatic Telephone Manufacturing Co.) Model, 
working on 24 volts. 
Experiment (a). Unsafe condition—A 500 ohm shunt, connected in 
parallel across the ends of the magnet windings, is disconnected by means 
of aswitch. Signalling by bringing wires in contact causes ignition. 
Experiment (b). Safe conditions —The 500 ohm shunt is connected across 
the coils. No ignition occurs on signalling. 
Experiment VI.—Experiment with clay and sand-clay stemmings. 
Blown-out shots are a possible cause of ignition and lead to loss of 
efficiency in the use of the explosives. It is found that sand-clay remains 
but clay is ejected as stemming—a mixture of sand and clay is actually 
used. 
Experiment. —Lead tubes, 2 ft. long and 2 in. bore by # in. wall are used. 
A wooden piston with a brass handle has been made to fit these tubes 
closely. When clay is packed into one of these tubes, little force is required 
to push the material through the tube. With sand, hammering of the piston 
produces a bulge of the lead wall and the sand is not ejected. 
Experiment VII.—Lamp testing experiments. 
A flame lamp (No. 2a Davis-Haydock pattern) is raised into mixtures 
containing from 1 to approximately 6-5 per cent. of methane in the Oldham 
chamber. ‘The mixtures are prepared by means of rotameters. 
As the percentage of methane in the air is raised from 1 per cent., the 
flame of the lamp becomes gradually higher and is finally extinguished in 
a mixture containing approximately 6 per cent. of methane. This latter 
mixture is ignited with a taper. 
Experiment VIII.—Showing that a lighted cigarette does not ignite a 6 per cent. 
methane-air mixture. 
