104 



Mr. J. LeConte 



The breaking of a glass vessel by a sudden shock communi- 

 cated by means of water is a fact long known, and is illus- 

 trated by the old familiar class experiment of exploding a 

 " Prince-Rupert drop " while its bulb is plunged into an ordi- 

 nary apothecary's phial filled with water. 



13. Experiments icith stout glass Tides. — The cylindrical 

 glass tubes employed were about 6 feet long and 1*5 inch 

 Fig. 2. 



in diameter, the glass being about 0*5 of an inch in thickness. 

 They were covered by pasting cartridge-paper over them, so 

 as to prevent the loss of fragments when breakage occurred. 

 (See tig. 2, M.) 



The tubes were adjusted to a framework of wood so arranged 

 (fig. 2, N) that they could be plunged in a horizontal posi- 

 tion beneath the surface of the water behind the pile, the axis 

 of the tube being at right angles to the plane of its shadow, 

 and held there (the observer standing as before on the top) 

 with the middle of the tube in the geometrical shadow, while 

 the two extremities projected on either side about 2*5 feet 

 beyond the boundaries of said shadow. (Fig. 3, C and (7.) 

 In every case the shock of the explosion shivered the pro- 

 jecting portions of the tube, and left the portion within the 

 shadow uninjured. The boundaries between the broken and 

 the protected portions of the glass were sharply defined. Vv 



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 framework 

 and tubes — adjusted at right angles to the plane of the pro- 

 longed shadow — into the water at this distance (12 feet) from 

 the obstacle which obstructed the sound-wave transmitted by 

 the liquid. (Fig. 3, 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 hori- 

 zontal glass tube was sensibly equal in length to the diameter 



