56 
occupies certain positions are known, i.e. the curves repre- 
senting the velocity and acceleration of the point may he 
drawn from the curve representing the positions of the 
point. Also a converse method by which the position of a 
point at any time may be found from the curve representing 
either its velocity or displacement. 
" On Explosions of Fire Damp.” 
E. W. Binney, V.P., F.B.S., said that the fearful loss of 
life in our coal mines deserved the careful attention of all 
societies like ours. It ought to be one of the objects of 
science to endeavour to find out the cause of these explo- 
sions and to devise some means to prevent their occurrence 
or lessen their frequency. No doubt Government Inspec- 
tion had been of service, and the examination of managers 
would tend to improve the efficiency of mining officers; but 
still notwithstanding these improvements the explosions of 
fire damp are sadly too frequent. The lamentable events 
which have taken place during the last ten days clearly 
show that they sometimes occur without any great change 
in the barometric pressure of the atmosphere, although 
undoubtedly sudden depressions in a barometer ought to 
caution miners against emission of gas from the seam of coal 
and coal wastes, and put the men more on their guard at 
such times. 
It has been stated in this society that certain conditions 
of the atmosphere quite irrespective of barometric pressure 
may have something to do with causing the “ drag” in the 
currents of air circulating through a mine, as explosions 
have frequently occurred during an east wind and a muggy 
state of the atmosphere, and a vesicular condition of water 
in the air has been suggested as the probable cause of this 
lessening of the speed of the air passing through the galle- 
ries of mines. Now, careful observations with a good 
anemometer in the return air course of a mine ought to 
