6 REPORT ON THE RELATION BETWEEN 



December, is due chiefly to the frequent and sudden diminutions of atmo- 

 spheric pressure which accompany the storms that prevail during these 

 months. 



The advent of a cyclone to Britain produces both the meteorological 

 conditions which tend to make the atmosphere of a mine explosive. The 

 barometer falls and the thermometer rises. The examination of particular 

 instances of explosions will show that both causes frequently concur in pro- 

 ducing them. But from March to August a rising thermometer is the ex- 

 ponent of danger from the predominating meteorological agent, and a, falling 

 barometer is the corresponding exponent from August to January; while the 

 curves indicate that the increased activity of the effective ventilation renders 

 January and February a period of comparative safety, so far as atmospherical 

 influences are concerned. 



The list of dates of colliery explosions begins in 1743, and often presents 

 a hiatus of four or five years in its earlier portion, when collieries were few, 

 and the more fatal cases only were recorded. Of the 514- cases in my list, 

 considerably more than one-half have occurred during the last five years. 

 The rate of increasing carefulness in observing and publishing such cata- 

 strophes, may be estimated by the numbers of known explosions for each 

 year since 1849. These were— 22 in 1850 ; 53 in 1851 ; 67 in 1852 ; 75 in 

 1853, and 77 in 1854. Old meteorological registers are also much less com- 

 plete than those of recent years. 



The most satisfactory method, therefore, of forming a correct opinion of 

 the nature and extent of meteorological influences in producing an explosive 

 atmosphere in mines, would be to take, as a standard of comparison, the 

 barometrical and thermometrical curves for the last five or six years, con- 

 structed from several daily readings made at some observatory situated near 

 the centre of the colliery districts. 



By way of illustration, I shall examine the meteorological conditions which 

 were simultaneous with, or which immediately preceded, the explosions in 

 British coal-mines during the end of 1851 and the whole of 1852. I have 

 taken the Greenwich Observations for 1851 ; and for 1852 the Manchester 

 Observations, which were laid before the Parliamentary Committee of 1854 

 by Mr. Dickenson, Government Inspector of Mines. The Manchester obser- 

 vations have been carefully compared with the contemporaneous observations 

 at the Royal Observatory at Greenwich, and those made at Highfield House, 

 near Nottingham, by Mr. Lowe. 



In all the curves 1 have drawn the vertical fluctuations of the barometer 

 of the actual size, and those of the thermometer to a scale of 10° to an inch. 

 The barometrical line of 30 inches coincides with the thermal line of 70° ; 

 except during the first three mouths of 1852, when it coincides with the 

 thermal line of 60°, in order to save space. 



The upper thermal line indicates the diurnal, and the Imoer the nocturnal 

 temperature. 



In the continuous curves for 1851 and 1852, each day is represented by a 

 lateral space of -Jgth of an inch, but in the barometrical curves of isolated 

 cyclones, by -Joth of an inch. 



In the vertical strip denoting a day of explosion, the space between the 

 barometric curve and the line of 30 inches is shaded, as also the space 

 included between the two thermal lines ; the shade being deeper where more 

 explosions than o.:e occur on the same day. This aiTangement enables the 

 eye to perceive readily the height of the barometer, and the height and range 

 of the thermometer on the day of explosion ; and to compare them with those 

 of the preceding days. 



