4 REPORT ON THE RELATION BETWEEN 



inflammable carburetted hydrogen gas oozes out from the coal into the mine 

 in greatest abundance (and, therefore, that the danger of explosion is great- 

 est) when the barometer has fallen considerably, and a toarm wind blows 

 from the south-east, south, or south-west points of the compass ; and that, 

 on the contrary, the mine is most free from gas, and explosions are least fre- 

 quent, when the barometer is high and the wind cold and northerly, 



A brief exposition here, of the general nature of the great storms which 

 pass over the British Islands and the continent of Europe, will help to a right 

 understanding of the special cases to be afterwards considered ; and will also 

 show that the several meteorological conditions which have been so often 

 observed to precede, or accompany, a highly inflammable state of the atmo- 

 sphere of a coal-mine, are only so many direct consequences of the "Law of 

 Storms " in the Northern Hemisphere. 



From the valuable work of Colonel Reid " On the Law of Storms and of 

 the Variable Winds" (Weale, London, 1849), it appears that the great 

 storms which sweep over Britain and the Continent of Europe during the 

 autumnal and winter months, rise first among the West Indian Islands; and 

 after coasting along the sea-board of the United States, cross the Atlantic 

 Ocean in a north-easterly direction. 



These storms are simply immense aerial eddies, or whirlwinds, which ex- 

 pand gradually as they proceed ; their mean diameter frequently extending 

 a thousand miles by the time that they impinge upon Ireland and the western 

 coast of Scotland, England, and France. In the course of a few days, such 

 a storm passes over France and the British Isles, to Belgium, Holland, Ger- 

 many, Denmark, Sweden, and the Baltic Sea (Plate I.). 



The atmospheric pressure diminishes continuously, but at an accelerated 

 rate, from the circumference towards the centre of a revolving storm. Hence, 

 if a chord be drawn parallel to the track of the centre, to represent the part 

 of the storm that passes over any assigned place, the mercury at that place 

 ■will fall until the middle of the chord arrives there ; and will rise, at first 

 rapidly, but afterwards more and more slowly, as the second half of the storm 

 is passing over. It follows that the greatest local depression of the mercurj' 

 •will occur simultaneously at all places situated on the diameter perpendicular 

 to the track of the cyclone. 



In the cyclones of the Northern Hemisphere, the wind turns m a direction 

 contrary to the motion of the hands of a watch, so that when a revolving storm 

 approaches Britain, the mercury begins to fail, and a t^arraitmc? to blow from 

 the soiithward. These are precisely the circumstances under which expert' 

 ence has proved that coal-mines are most liable to explosion. 



As the diameter of simultaneous local maximum depression advances, the 

 mercury falls faster at any place in front of the storm, and the violence of the 

 wind increases there. 



The general track of cyclones passing over Britain tends towards the 

 E.N.E. Therefore, if the storm begins at S.E., S., and S.W. respectively, at 

 three different places, the wind ivill shift during the transit of the cyclone, 

 from S.E. through E. to N. at the first place; from S. through W. to 

 N.W. at the second place ; and from S.W. to W. at the third place. 



This shifting of the wind, which indicates a passing cyclone, is reckoned 

 by miners among the symptoms of danger. J. Roberts, Esq., Colliery Owner 

 in Dean Forest, stated before the Committee of 1849 (Qu. 6272) that the 

 gas in those mines generally occurs as the wind shifts. 



The diagram (Plate I.) is adapted from the Chart at page 323 of Colonel 

 Reid's work, and represents the storm of November 1838. I have added 

 the mean direction (E.N.E.) of progression, and drawn chords through 



