Sound-Shadows in Water. 



103 



water along the cylinder of wood. The concussion produced 

 by such an explosion was so violent that it killed or stunned 

 the fish in the water within a radius of 200 or 300 feet from 

 the explosive centre. They rose to the surface in a helpless 

 condition, and were secured by the boys. 



EXPEKIilEXTS ON SOUND-SHADOWS. 



12. Experiments with stout glass {soda-water) Bottles.— hi 

 these experiments the observer stood on the top of a vertical 

 cvlindrical pile (the trunk of an Oregon pine) about one foot 

 in diameter, situated about forty feet horizontally from the 

 explosive cartridge. The bottle, being secured to a rigid rod, 

 was first plunged under the water from ten to twelve inches 

 behind the pile (fig. 1, A), that is within its geometrical 

 shadow. The shock of the explosion did not injure the bottle. 

 It was then plunged into the water in front of the pile (fig. 1, 

 B), or outside of its geometrical shadow. In this position 

 the bottle was shivered to atoms by the concussion due to the 

 explosion. As viewed from the experimenter's situation on 

 the top of the pile, fig. 1, A' and B' indicate the two positions 

 of the bottle in the preceding experiments. 

 Fir. 1. 



Ob' 



The experiments were varied by plunging bottles into the 

 water in various positions around the pile, within and outside 

 of its geometrical projection from the explosive centre ; and 

 in all cases they were protected from injury when within the 

 geometrical shadow, and were shivered when outside of the 

 same. The same results took place whether the bottles were 

 filled with water or with air. 



