Unfortunately, Professor Boys’s apparatus did not work satisfactorily, but a most interesting series of pictures was secured by the kinematograph. This instrument had been constructed especially for taking pictures at a very high rate of speed, viz., eighty exposures a second, or four times the usual number. The sound wave appears in the first dozen pictures as a hazy ring of light, opening out from the center of explosion. The ring, though not very conspicuous when the pictures are viewed singly, becomes a striking object when they are projected in rapid succession on the screen. We see the rush of smoke along the ground to the box in which the explosion is confined (the smoke of the quick fuse); then comes the burst of the explosion with such startling reality that we involuntarily jump. The image of the sound wave flies out in the form of a white ring, and is gone in a moment; and there remain only the rolling clouds of smoke. It is interesting to observe the development of the explosion by running the machine quite slowly, and by thus magnifying time to follow the changes which ordinarily occur in such rapid succession that the eye is unable to perceive them. Of this series of pictures, Professor Boys says: “The kinematograph fails to show any _black_ ring; and this is not surprising, as with the exposure of about one one hundredth of a second the shadow would have to be at least eleven feet thick in order that some part should remain obscured during the whole exposure. As a fact, there is clearly seen a circular light shading, which does--so far as one can judge from the supposed rate of working and the known distances--expand at about the same rate as the observed shadow, but it is lighter than the ground and shaded, instead of being dark and sharp, as seen by the eye.” [Illustration: KINETOSCOPE FILM OF EXPLOSION.]