486 Prof. F. Clowes. [Feb. 2, 



they do not publish any further account of its indications, appa- 

 rently because their attempt to introduce the hydrogen flame into a 

 safety-lamp was altogether unsuccessful. 



Pieler was also so much impressed with the advantages obtained 

 by the use of a hydrogen flame for gas-testing, that, failing to apply 

 this flame to a portable lamp, he still recommended (loc. cit.) the 

 application of the hydrogen flame, fed by a chemical generator, in a 

 stationary apparatus above ground, to testing samples of mine-air 

 which were conveyed to it. He confesses that his alcohol-lamp is 

 only a substitute for the impossible hydrogen- lamp, which he would 

 evidently recommend if it were available. The alterations recently 

 made by M. Chesneau (' Annales des Mines,' August, 1892, p. 203) 

 in the Pieler lamp would therefore probably not have been recom- 

 mended by the original inventor of the alcohol lamp, if a portable 

 hydrogen lamp had been in existence ; and although they add to the 

 safety of the lamp, they do so by rendering the lamp self-extinguishing 

 in moderately high percentages of gas. The extinction of the testing- 

 lamp is a serious inconvenience to the gas-tester, and will not prove 

 to be a recommendation to him. 



The Pieler lamp further labours under the serious disadvantage 

 that the pale caps have to be observed through wire gauze, which 

 obstructs much of their light. The caps become actually invisible 

 if the gauze around the lamp is bright and reflective, as it frequently 

 is in a new lamp. 



When samples of air can -be conveniently collected and carried to a 

 testing station, no arrangement will be found more convenient and 

 delicate than a hydrogen flame of standard size, fed by a large 

 cylinder of the compressed gas. The flame-cap is then observed in 

 a dark room against a dead- black ground, and its height is noted. A 

 portable hydrogen safety-flame will, however, be found to be much 

 more convenient, as it can be carried to the spot where the test is to 

 be made. The troublesome collection and transport of bulky air 

 samples are thus avoided. 



A Portable Safety-lamp with interchangeable Oil and Hydrogen 



Flames. 



An arrangement for introducing a standard hydrogen flame into 

 any ordinary form of safety-lamp has been already described (' Roy. 

 Soc. Proc.,' vol. 51, p. 90). The requisite supply of hydrogen was 

 contained in a compressed state in a steel cylinder, which was 

 similar to those in common use, but of much smaller dimensions. 

 The cylinder was slung from the shoulder by a strap, and was con- 

 nected when necessary with the lamp by means of a length of 

 flexible tubing. On slightly opening the valve of the cylinder, the 



I 



