450 Mr. W. Galloway on Safety -Lamps. [June 18, 



(2) Between A and L : 



At 33 ft. 8 measures = 2' 184 grammes 

 61 ft. 8 2-184 



96 ft. 8 2-184 



It is remarkable that, in these latter experiments, it was not necessary 

 to increase the quantity of gunpowder as the distance from the lamp was 

 increased. The large charge required at the first station seems to have 

 been owing to the presence of the manhole between the lamp and the 

 point at which the shot was fired ; but this waste of energy having been 

 provided for, no further addition to the charge was required. It would 

 seem as if part of the energy of the sound-wave was expended in the 

 space C L in shaking the brickwork and a narrow wooden gangway 

 supported on cross-pieces at a height of 1 ft. 5 in. from the sole; 

 whereas in the space A L, in which no gangway had been laid down, it 

 was conveyed through the tunnel in the solid rock without much loss of 

 intensity. 



The temperature of the air in the sewer was 55-56 Fahrenheit ; and 

 there was generally a current travelling in the direction C to A at the 

 rate of 5 to 10 ft. per minute. 



These are the last experiments from which important results have been 

 obtained ; they were concluded in November 1873. 



After this I made some experiments with firedamp in a stone-mine in 

 No. 2 Pit, Douglas, near Glasgow. 1 filled a sheet-iron box of 18 cub. ft. 

 capacity with firedamp at the borehole in the C Pit of Hebburn Colliery, 

 and brought it to this mine. As the gas appeared to have become mixed 

 with air through leakage during the transport, and would not burn 

 satisfactorily in the lamp of the apparatus (fig. 1, Plate VI.), the apparatus 

 shown in fig. 7, Plate VII., was constructed. Two boards, each of an 

 inch thick, and of the shape and dimensions of the top of the apparatus, 

 are joined together by iron rods of an inch in diameter, one at each 

 angle. A sheet of india-rubber, -% of an inch thick, is then fastened 

 round the frame thus formed by nailing it to the boards, and an isolated 

 space of the form d, fig. 7, is obtained. An opening, 1| inch in diameter, 

 in the upper board serves as an outlet for the products of combustion ; 

 and a similar opening in the lower board serves as an inlet for fresh air 

 and the firedamp from a Bunsen burner. This apparatus is placed on 

 two legs fastened to one of the sleepers in the roadway, and it is stayed 

 tightly before and behind by four stout wires in positions analogous to s, 

 the only one that can be seen in the figure. 



A Davy lamp was lighted and placed in the inside of d, on a block of 

 wood 3 inches high by 3 inches in diameter, so as to have its wire gauze 

 as near as possible to the centre of the space ; firedamp was then admitted 

 at the lower opening, and the draught was regulated at a. The appear- 

 ances presented by the lamp were observed through a glass window, h, 

 fastened in the sheet of india-rubber ; and as soon as the flame showed 



