No apology can be needed in such a district as this for introducing the subject which forms the title of this paper, but I must disclaim any pretension to possessing superior information upon it. Having the pleasure of Mr. Ansell’s acquaintance, I have agreed to become, though very imperfectly, his representative to-day, in order to bring his admirable invention under your notice. Dependent, as our national industries are, upon an adequate supply of coal, we are bound to consider the extraordinary perils which surround those who obtain it for us. Mr. Holland, one of the Royal Commissioners of Mines, has ascertained that explosions of fire-damp in coal mines cause 365 deaths per annum. Thus, we may say, that one life is lost every day throughout the year from explosions alone, but as this estimate was made two years ago, how much higher will be the figures that include the slaughter wrought by the late explosions at Barnsley and in Staffordshire. Out of the 1,644 lives sacrificed in 1864 to our necessity for coal, being at the rate of one life for every 109,715 tons raised, we cannot but feel that the accidents resulting from explosion are the most terrible of all, from their suddenness and the wholesale destruction which they deal, and we shall hardly divest ourselves of the unpleasant feeling that they arise from causes which ought to be preventible.* The subject will divide itself into two parts: Firstly, the scientific principles involved in Mr. Ansell’s method of detecting ...