MINING. 299 



increase of temperature take place together, the mine experiences 

 at the same time an augmented risk and a diminished power of 

 ventilation. But the relation between explosions and surface 

 storms was not accurately looked into before Mr. T. Dobson in 

 1855 presented a paper to the British Association at Glasgow. 

 More recently, in 1872, Messrs. R. Scott, F.R.S., and W. Galloway* 

 have shown so important a series of coincidences between colliery 

 explosions in the years 1868, 1869, 1870, and the weather condi- 

 tions as recorded at Stonyhurst, that they think their evidence 

 justifies the view that "meteorological changes are the proximate 

 causes of a large majority of the accidents." 



These instruments should, however, not be kept only in a 

 cabin underground, but should in duplicate be fixed up in some 

 thoroughly visible position in the office at the surface. And since 

 sudden variations, other than those due to depth, of the readings 

 of the one set of instruments from the other may be significant of 

 matters requiring instant attention, an apparatus admitting of com- 

 parison between the two may do good service. Thus an increase 

 of temperature beyond a certain limit may be the indication of 

 the approach to an outbreak of "breeding-fire" or spontaneous 

 combustion, and an abnormal decrease of barometric pressure 

 in the main return air-course will be apt to show that some obstruc- 

 tion has taken place in the interior air-ways. Mr. Alan Bagot ha-s 

 recently patented a variety of aneroid barometer and a metallic 

 non-mercurial thermometer which will fulfil the required condi- 

 tions by signalling, through aid of a battery, as soon as a certain 

 limit either of depression or temperature is attained by the index. 



Although practical reasons have interfered with its employment 

 in mines, the ingenious indicator of Mr. Ansell, for calling atten- 

 tion to the presence of fire-damp, even in minute quantities, 

 demands attention as a scientific instrument. 



Amongst other instruments which come into play in mining, 



* On the connection between Explosions in Collieries and Weather. Proc. 

 Royal Society, 1872, p. 292. 



