July 23, 1874 1 



NA TURE 



225 



the meshes of the wire-gauze in virtue of the vibration of 

 the molecules of the explosive gas. An explosion which 

 took place at Cethin Collier>' in 1S65 is a good example 

 of one that may have been caused in this way. Several 

 a'ays after the explosion the safety-knip of the overman 

 was found securely locked and uninjured, lying at a dis- 

 tance of a few yards within an abandoned stall which was 

 known to have contained firedamp. Shot-firing was car- 

 ried on in this mine, and it is not improbable that a sound- 

 wave from an overcharged or blown-out shot had passed 

 through this lamp and ignited the explosive mixture 

 shortly after the overman had entered it ; moreover, the 

 Inspector of Mines in his report says he has no doubt 

 that the gas in this state was ignited and was therefore 

 the origin of the explosion, but he is unable to state by 

 what means it was fired. 



A number of experiments were made by Mr. Galloway 

 in connection with this subject ; the cost of apparatus, 

 &c., was provided for by the liberality of the Government 

 Grant Committee of the Royal Society. 



The first experiment was made on Jan. 16, 1872, in the 

 physical laboratory of University College, London. A 

 sheet of wire-gauze i ft. square was inclined at an angle 

 of 70° and a slow current of gas and air from a Bunsen- 

 burner was directed against its lower surface ; part of the 

 explosive mixture passed through the meshes, and when 

 ignited produced a flat flame 3 in. long by I in. wide 

 about the middle of the upper surface of the wire-gauze. 

 A glass tube 3 ft. 4 in. long by about 3,! in. diameter was 

 placed horizontally with one end opposite to the flame on 

 the same side of the wire-gauze and distant from it about 

 \\ in. At the other end of this tube a sound-wave was 

 produced by the explosion of a mixture of coal-gas and 

 oxygen contained in soap-bubbles. When the sound- 

 wave passed through the tube the flame was carried 

 through the meshes of the wire-gauze and ignited the 

 gas issuing from the Bunsen-burner on the other side. 



Some experiments similar to the first were made in one 

 of the laboratories of the Royal College of Cliemistry in 

 Dec. 1S72. The glass tube was replaced by a tin-plate 

 tube about 20 ft. long by 2 in. diameter : paper and other 

 diaphragms were inserted at a distance of 10 ft. from the 

 origin of disturbance to insure that only a sound-wave 

 was propagated through the tube. The results were the 

 same as before. 



Two sets of apparatus, a larger and a smaller, were then 

 constructed ; in both the sound-wave of a pistol-shot is 

 conveyed through tin-plate tubes to a distance of about 

 20 ft., then it passes through a safety-lamp burning in an 

 explosive mixture. In the smaller apparatus the tube is 

 3 in. in diameter ; one end is closed by a disc of wood 

 with a hole in the middle large enough to receive the 

 Tnuzzle of a pistol; at a distance of 10 ft. from the disc 

 there is a diaphragm of sheet india-rubber, and at the 

 farther end is a safety-lamp with gas-flame. At the 

 Tjottom of the safety-lamp there is a circular chamber 

 with holes round about from which gas can be made to 

 escape, and when this gas, rising up, mixes with the air it 

 forms an explosive mixture surrounding the wire-gauze 

 cylinder. The pistol by means of which the sound-wave 

 is produced is charged with "205 gramme of gunpowder, 

 and a tamping paper is rammed down well upon the 

 charge. When the shot is fired through the hole in the 

 wooden disc, while the explosive mixture surrounds the 

 lighted safety-lamp, the flame is instantly carried through 

 the meshes by the vibration, and ignites the gas on the 

 outside. In the larger apparatus the tube is 8 in. in dia- 

 meter, and 21 ft. long ; at one end there is a wooden disc 

 as before ; at 20 ft. from the disc there is a sheet india- 

 rubber diaphragm, and the extreme end is closed by a 

 sheet of thin paper tied over it. Part of the last 12 in. 

 (thus isolated from the rest of the tube and from the 

 exterior) is enlarged sufficiently to hold a safety-lamp, and 

 it is provided with an inlet below for air or air and gas. 



and a chimney above for the sake of the products of 

 combustion. A lighted Davy or Clanny lamp cf ordinary 

 construction having been placed in this space, gas is 

 made to mix with the air which flows up through it in 

 consequence of the draught caused by the lamp; the 

 appearances presented by the flame arc observed through 

 a small glass window, and when they indicate that the air 

 is explosive the shot is fired. The flame within the safety- 

 lamp is passed through the meshes, explodes the mixture 

 in the isolated space, blowing out the paper end, and, 

 passing backwards through the inlet, ignites the gas 

 where it first mixes with air. In this case the shot 

 consists of -41 gramme of gunpowder tamped as before. 



The lamps that were tested in this apparatus arc those 

 known as the Davy, Clanny, Stephenson, Mueseler, and 

 Eloin. The flame was easily passed through the Davy 

 lamp, with rather more difficulty through the Clanny, and 

 not at all through any of the others. 



The first experiments with these two sets of apparatus 

 were made in January and February 1873, at the Mete- 

 orological Office, where Mr. Scott most kindly provided 

 accommodation : the experiment with the smaller appa- 

 ratus was shown at the Royal Institution, by Mr. Spottis- 

 woode, on the evening of Jan. 17 ; and afterwards at 

 one of the Cantor Lectures of the Society of Arts, by the 

 Rev. Arthur Rigg. The next experiments were made in 

 No. 7 Pit, Barleith, near Glasgow, with firedamp from a 

 blower, but the flame could not be passed through the 

 safety-lamps on account of the impurity of the gas, which 

 contained only 75 '86 of light carburetted hydrogen. The 

 last experiments were made in the C Pit of Hebburn Col- 

 liery, near Newcastle- on-Tyne, also with firedamp from a 

 blower, and as the firedamp was very explosive, the flame 

 was easily passed through the Davy-lamps of each 

 apparatus. 



After this, experiments were made on a larger scale in 

 part of a new sewer in North Woodside Road, Glasgow. 

 The sewer is ovoid in section; it is 6 ft. high and 4ft. 

 wide at its greatest dimensions ; part of it is a tunnel in 

 the solid rock, part is built in brickwork through surface- 

 drift. The gas safety-lamp of the smaller apparatus was 

 placed on a board fi.xed across the sewer at a height of 

 2 ft. 8 in. from the bottom, and surrounded v,-ith an explo- 

 sive mixture of coal-gas and air in the same way as when 

 it was used in connection with the tin-plate tubes. Shots 

 were fired from a pistol at certain distances from the 

 lamp (the details of the distances and the charges re- 

 quired to pass the flame in the paper and sections of the 

 sewer are given in the plites which accompany it). One 

 hundred and nine feet was the greatest distance available 

 in the part built of brick, and at this point a sound-wave 

 of sufficient intensity to p3S5 the flame was produced by 

 firing a charge of 3'S82 grammes = 59 grains of gun- 

 powder. At 96 ft. from the lamp a charge of 3'276 

 grammes was required when the sound-wave passed 

 through the brickwork tunnel all the way, and 2184 

 grammes when it passed through the tunnel in the solid 

 rock. These experiments seem to be perfectly conclu- 

 sive. 



Mr. Galloway's discovery — that when the vibration of 

 the air which constitutes a sound-wave has a certain 

 amplitude, it can transmit flame through the wire-gauze 

 ot the Davy and Clanny lamps — famishes an additional 

 argument against retaining these lamps in use, at least 

 in the hands of ordinary workmen. On Dec. 15, 

 1815, Davy said he was convinced that, as far as ven- 

 tilation was concerned, the resources of modern science 

 had been fully employed ; he then proceeded to 

 describe a " safety lantern," which is identical in prin- 

 ciple with the Stephenson lamp, and is extinguished in 

 an explosive mixture (Phil. Trans. 1816, p. 2). This 

 "safety lantern "was afterwards discarded in favour of 

 the Davy lamp proper, the principal advantage of which 

 was stated to be that it would not only preserve the col- 



