Many of the victims of the dynamite explosion, a year or two ago, in the London Underground Railway, are said to have lost the drum of one ear only, that nearest to the source. This seems to point to a projectile, not an undulatory, motion of the air and of the gases produced by the explosion. So long, in fact, as the disturbance travels faster than sound, it must necessarily be of this character, and would be capable of producing such effects.

Another curious fact apparently connected with the above is the (considerable) finite diameter of a flash of forked lightning. Such a flash is always photographed as a line of finite breadth, even when the focal length is short and the focal adjustment perfect. This cannot be ascribed to irradiation. The air seems, in fact, to be driven outwards from the track of the discharge with such speed as to render the immediately surrounding air instantaneously self-luminous by compression.