John LeConte—NSound-Shadows in Water. 38 
case the shock of the explosion shivered the projecting portions 
of the tube, and left the portion within the shadow uninjured. 
The boundaries between the broken and the protected por- 
tions of the glass were sharply defined. 
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ae 
‘By standing on the top of a second pile, in the direction of 
the axis of the shadow of the first pile, and distant about 12 
feet, the experiments were varied by plunging the frame-work 
and tubes—adjusted at right-angles to the plane of the pro- 
longed shadow—into the water at this distance (12 feet) from 
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s==_~==-  SANO-STONE REEF 
the obstacle which obstructed the sound-wave transmitted by 
the liquid. (fig. 83, D and D’). The shock of the explosion 
produced sensibly the same results as when the tube was near 
to the obstructing obstacle:—the protected portion of the hor- 
Zontal glass tube was sensibly equal in length to the diameter 
Am. Jour. oo Series, VoL. XXIII, No, 133.—Janvary, 1882. 
