252 COLLIERY EXPLOSIONS AND THE WEATHER OF 1885. ANON. 
observations at the Karwin mines is "That where, after a rapid rise 
of the barometer, it continued to rise slightly, or remained stationary 
for some time at its maximum, a gradual increase in the volume of 
gas in the air would set in ; or if, after a rapid fall in the barometer, 
it continued to fall gradually, or remained stationary at its lowest 
point, a decrease in the quantity of gas would become apparent." The 
results of the two distinct series of observations at Seaham and 
Karwin completely justify the system adopted in the colliery warnings 
before the observations were commenced. 
The question naturally arises — How are we to explain the seem- 
ing contradiction of the laws of pressure on gasses ? A year ago it 
was suggested that the real explanation will probably be found in the 
supposition that the earth's thin crust feels the changes of atmos- 
pheric pressure, the undulations, perhaps, being very slight of them- 
selves, but sufficiently marked to affect the presence of gas in faults 
and other reservoirs at no great distance from the surface. We know 
that a rise of one inch in the barometer causes the surface of the sea 
to be depressed a little more than one foot. Japan feels many earth- 
quakes during the year, but the great majority of them take place in 
winter when the barometer is high, not one-third of the shocks 
occurring in summer when pressure is low. 
Finally we come to the question of coal-dust. It is now generally 
recognised by those who have studied the subject that tlie severest 
explosions occur in dry, dusty mines, the impalpable dust particles 
floating in the air being a means of propagating an explosion to 
long distances from the seat of origin. Xow, if we consider the 
matter, it will be admitted that so far as this element of danger is 
concerned, an anticyclonic distribution of pressure favours greater 
violence in explosions from the fact that, generally speaking, a high 
barometer accompanies a dry atmosphere, which would render the 
coal-dust more inflammable than with dampness. It becomes necessary, 
therefore, to impress upon colliery officials both gas and dust become 
dangerous many hours, sometimes days, earlier than is generally 
accepted. 
It is, perhaps, a little risky to make any prediction as to the 
future, but it is interesting to notice in the following table that, 
