484 



Prof. F. Clowes. [Feb. 2, 



February 2, 1893. 

 Sir JOHN EVANS, K.C.B., U.C.L., LL.D., Treasurer, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The following Papers were read : 



1. "A New Portable Miner's Safety-lamp, with Hydrogen 

 Attachment for Delicate Gas-testing; with Exact Measure- 

 ments of Flame-cap Indications furnished by this and other 

 Testing Lamps." By FRANK CLOWES, D.Sc. Lond., Pro- 

 fessor of Chemistry, University College, Nottingham. 

 Communicated by Professor ARMSTRONG, F.R.S. Received 

 January 10, 1893. 



Introductory. 



The presence of firedamp is still almost invariably detected, and 

 its amount is more or less accurately measured, by the observation of 

 the pale blue " cap " produced by the " gas " over the flame of the 

 safety-lamp. By suitably reducing the flame of an ordinary oil 

 safety-lamp by drawing down the wick, it is generally considered 

 that percentages of gas in the air varying from about 2'5 to 6 can be 

 detected and estimated. The upper limit is that at which an inflam- 

 mable mixture is approached. The lower limit reached by this 

 method of testing is, however, not considered sufficiently low, and for 

 two reasons. W. Galloway has shown (' Roy. Soc. Proc.,' vol. 24, 

 p. 361) that air containing less than 1 per cent, of gas becomes 

 explosive when it is mingled with fine coal-dust ; hence the ordinary 

 safety-lamp test for gas is incapable of indicating a dangerous state 

 of the atmosphere in dusty mines. And, further, even in the 

 absence of coal-dust in the air of the mine, it is necessary to test the 

 " returns," or the ventilation currents as they leave the working 

 "districts" and the mine, in order to ascertain whether the general 

 ventilation of the mine is well distributed and sufficient. It is stated 

 by high authorities that the " main return " air should not contain 

 more than 0'5 per cent, of "gas," and that 1 per cent, should never 

 be reached. An ordinary oil safety-lamp gives no indications with 

 1 per cent, or less of gas. 

 During the last twelve years several forms of gas-testing apparatus 



