FIRE-DAMP INDICATOR 



With Falling Barometer. 

 Carbonic Acid. 



Inches. 

 1 per cent. = 0-0 15 



It is imperative that the instrument be held by the ring handle, else its action 

 cannot be depended on. Mr. Ansell has found that the following figures are to be 

 relied upon for fire-damp, and for carbonic acid : 



With Rising Barometer. 



Fire-damp. 



Inches. 

 1 per cent. = 0-0 10 



= 0-030 3 =0-050 



= 0-060 5 =0-080 



= 0-080 10 =0-160 



= 0-090"| 15 =0-240 



= 0-130 l' 20 =0-330 



= 0-170 f ^ 50 ., =0-820 



= 0-220 J 8 100 =1-640 



= 0-320 

 = 0-800 

 = 1-680 



Mr. Ansell was much assisted by Mr. Thomas W. Short (of the firm of Short and 

 Mason, 62 Hatton Gfarden, E.G.), who practically realised the ideas Mr. Ansell con- 

 veyed to him, and so produced the apparatus in a simple and practical form. 



The following actual experiments were made by Mr. Ansell in a coal-pit at the 

 Ince Hall Colliery, on the 7th June, 1866, in the presence and with the assistance of 

 some officials of the Ince Hall Colliery Company. 



Two aneroid barometers were used, each with tiles of different thicknesses, with a 

 view to determine the proper thickness. The instrument denoted by the * had the 

 thinner tile. 



Note. It was remarked by the underviewer, that the lamp indicated a varying 

 amount of gas within a few seconds at the same place. These changes were attri- 

 buted to the heat from our 'lamps and from our bodies; and it was found that the 

 lamps and indicators most nearly agreed when both were taken into the gas at the 

 same instant. 



It was agreed that this was held 10 seconds too long, as the index-hand travelled backwards. 



