1874.] Mr. W. Galloway on Safety -Lamps. 415 



On the 16th of January, 1872, 1 made the first experiment in connexion 

 with this subject in the Physical Laboratory of University College, London : 

 Professor Gr. C. Foster was present and co-operated with me. A sheet 

 of wire gauze, 1 foot square, was inclined at an angle of 70, and a slow 

 current of gas and air from a Bunsen burner was directed against its 

 under surface. Part of the explosive mixture thus formed passed through 

 the meshes, and, when ignited, produced a flat flame on the upper surface 

 3 in. long by 1 in. wide, and symmetrically situated in regard to the 

 sides of the sheet. A glass tube, 3 ft. 4 in. long by 3 1 in. diameter, was 

 placed with one end at a distance of 1| in. from the upper surface 

 of the sheet of wire gauze; its axis was horizontal, passed through 

 the middle point of the flat flame, and was at right angles to the 

 line of intersection of a horizontal plane with the sheet. At the end of 

 the tube furthest from the wire gauze, a vessel, 3| in. diameter, containing 

 a solution of soap in water was placed ; the point at which the axis of 

 the tube cut the perpendicular from the centre of the liquid was 2| in. 

 from the end of the tube, and at the same distance above the surface of 

 the liquid. An explosive mixture of coal-gas and oxygen was forced 

 into the solution of soap until bubbles containing about 2 cub. inches 

 had formed on the surface. A light was then applied to the gas 

 at the upper surface of the wire gauze, and immediately afterwards 

 to the bubbles ; and after the explosion it was found that the flame had 

 vanished from the upper surface, and that the gas issuing from the 

 Bunsen burner was on fire. 



In December 1872, I made a number of experiments similar to the 

 foregoing in the Laboratory of the Royal College of Chemistry, when I 

 was much indebted to Dr. Erankland for his valuable suggestions. The 

 glass tube of the first experiment was replaced by two tin-plate tubes, 

 each 2 in. diameter (one 10 ft. 11 in., the other 9 ft. 7 in. long) ; they 

 were joined to form a continuous tube 20 ft. 6 in. long. The vessel 

 containing the solution of soap was small enough to be placed just inside 

 of one end of the tube, and the sheet of wire gauze was at a distance of 

 1 in. from the other end. The same explosive mixtures were again 

 employed, and the same result was obtained as before. A diaphragm, 

 consisting of four sheets of brown paper of ordinary thickness, was now 

 inserted at the junction of the two tubes ; the centre of the diaphragm 

 was bulged to a distance of about half an inch towards the origin of dis- 

 turbance. After the passage of the sound-wave, it was found that the 

 flame had shifted to the opposite side of the wire gauze, and the dia- 

 phragm was bulged to about the same extent, but in the opposite direc- 

 tion. A quantity of loose cotton-wool, sufficient to fill the end of the 

 tube completely for a length of three inches, was then pushed into 

 the end of the one furthest from the wire gauze, at its junction with 

 the other. After the sound-wave had passed, the flame was again 

 found to have removed to the opposite side of the wire gauze, and the 



