280 FRAGMENTS OF SCIENCE 



the sides of the bell, and not ita mouth, emitted the strong- 

 est sound, their practice being probably determined by this 

 knowledge. Our slabs of gun-cotton also emit waves of 

 different densities in different parts. It has occurred in 

 the experiments at Shoeburyness that when the broad side 

 of a slab was turned toward the suspending wire of a sec- 

 ond slab six feet distant, the wire was cut by the explo- 

 sion, while when the edge of the slab was turned to the 

 wire this never occurred. To the circumstance that the 

 broad sides of the slabs faced the sea is probably to be 

 ascribed the remarkable fact observed on March 23, that 

 in two directions, not far removed from the line of fire, the 

 gun-cotton 'detonated in the open had a slight advantage 

 over the new gun. 



Theoretic considerations rendered it probable that the 

 shape and size of the exploding mass would affect the con- 

 stitution of the wave of sound. I did not think large rect- 

 angular slabs the most favorable shape, and accordingly 

 proposed cutting a large slab into fragments of different 

 sizes, and pitting them against each other. The differences 

 between the sounds were by no means so great as the dif- 

 ferences in the quantities of explosive material might lead 

 one to expect. The mean values of eighteen series of ob- 

 servations made on board the " Galatea," at distances vary- 

 ing from If mile to 4*8 miles, were as follows: 



Weights . . . 4 oz. 6 oz. 9 oz. 12 oz. 

 Value of sound . 3-12 3-34 4-0 4-03 



These charges were cut from a slab of dry gun-cotton 

 about If inch thick: they were squares and rectangles of 

 the following dimensions: 4 oz., 2 inches by 2 inches; 



