THE ABERRATION OF SOUND 
249 
able that for some distance from the source the motion is of a 
projectile character.”* 
The breaking of the transoms over doors, while the window 
w'as uninjured, and the breaking of the windows unexposed to 
the direct force of the explosion are very interesting phenomena, 
and I wish to otTer an explanation which I think will account 
for the facts observed. The path of the maximum of disturb- 
ance results largely from the unequal resistance of the air, and 
while at the actual center of explosion the pressure may be in 
“ concentric shells,” at a very short distance it becomes stellar. 
The changing pressure of the wind, as shown b^^ Professor Lang- 
ley’s experiments, and the shape of the flame in an explosion 
(stellar) lead one to this conclusion. As the maximum wave 
moves from the focus, the air forming it is constantly changing, 
and the following sketch illustrates the path of an air particle 
as I believe it to be : 
A, B, and Care air particles in the })ath of a maximum wave 
traveling along the line 0 P. The motion of each is first along 
the line of 0 P, away from the focus, a result of direct imj)act of 
other particles, then back to its original i)osition, or near it. the 
track forming a closed curve. When the ])article is in the posi- 
tion A', B\ or C', its motion is toward the focus of the explosion, 
and so any damage it might do would be evidenced I)}" a break- 
ing of objects unexposed to the force of the direct wave. In the 
case of the transoms mentioned above, the back thrust which 
bnjke the glass and frame was cushioned by the air in the room, 
and so the window was not injured. 
* Eneyclop-cdia firitannicn, ninth eilition, vol. x.xiv, p. 418. 
