1874.] Mr. W. Galloway on Safety-Lamps. 447 



on the outside of the lamp*. If the charge of gunpowder be increased 

 to -272 gramme, or be decreased to -136 gramme, the experiment does 

 not succeed ; and if the wire gauze has become smoked by the flame of 

 the inner jet being too large, the flame cannot be passed through. 



In the apparatus represented in fig. 2, there are again two tin-plate 

 tubes, each 10 ft. long by 8 in. diameter, but they are joined to form one 

 continuous tube 20 feet long. At the end o there is a disk of wood, 

 5 in. thick, wifti a hole in the centre for the muzzle of the pistol. The 

 tube b (figs. 2 & 3), of tin plate, 12 in. long, has its interior isolated by 

 an india-rubber sheet tied over the end c, and a sheet of paper tied over 

 the end k. A ring, with a network of wires J in. thick, and with meshes 

 | in. square, is drawn over the diaphragm in the same way as in the 

 apparatus already described. Two short tubes, of 6 in. diameter, are 

 , joined to 6 to form a chamber large enough to receive a safety-lamp ; 

 they are closed by flat ends, with the exception of a hole 3 in. diameter 

 in the upper one, opening into a chimney 0, and an opening of 2 ip. 

 diameter into the tube / in the lower one. The upper end of the tube 

 / opens into a flat round chamber, with holes | in. diameter and | in. apart 

 round about its outside ; its position is indicated by the dotted line in 

 fig. 3. At the top of the chimney e there is a draught regulator, g, 

 which can be raised or lowered by means of the screwed spindle which 

 supports it. The safety-lamp to be tested is placed on the discoid 

 chamber, with its top projecting into the chimney if it is so long. Gas 

 is supplied by a Bunsen burner at the bottom of the tube /, and, mixing 

 with air, it flows upwards through the discoid chamber into the isolated 

 space around the lamp. The products of combustion pass upwards 

 through the chimney. 



The experiment is made thus : The pistol is loaded with *41 gramme t 

 of gunpowder in the same way as before : an ordinary Davy or Clanny 

 lamp is lighted and put into the space cZ, which is afterwards closed at 

 the ends. Gas is then made to flow into the tube /; the lamp is observed 

 through the window h, and as soon as it is seen that the atmosphere in the 

 space d is explosive, the shot is fired at o. The paper at "k is blown out and 

 set on fire ; and the flame of the explosive mixture, passing backwards 

 down the tube /, ignites the gas escaping from the Bunsen burner. 



The lamps which were tested with this apparatus are those known as 

 the Dary, 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 firedamp were made in No. 7 Pit, Barleitb, 

 near Glasgow. A wooden plug, with a small pipe through it, was driven 



* This experiment was shown by Mr. Spottiswoode at the Koyal Institution on the 

 evening of the 17th of January, 1873, with the apparatus I have described. The same 

 apparatus was afterwards used at one of the Cantor Lectures of the Society of Arts. 



f If the charge be made greater or less than this by -15 gramme the experiment 

 does not usually succeed. 



