2G4 FRAGMENTS OF SCIENCE. 



the one side and 20 on the other side of the line of fire. 

 The shots were heard by eleven observers on board the 

 Galatea,' which took up positions varying from 2 miles 

 to 13J miles from the firing-point. In all these obser- 

 vations, the reinforcing action of the reflector, and of 

 the parabolic muzzle of the gun, came into play. But 

 the reinforcement of the sound in one direction implies 

 its withdrawal from some other direction, and accord- 

 ingly it was found that at a distance of 5J miles from 

 the firing-point, and on a line including nearly an angle 

 of 90 with the line of fire, the gun-cotton in the open 

 beat the new gun; while behind the station, at distances 

 of 8^ miles and 13J miles respectively, the gun-cotton 

 in the open beat both the gun and the gun-cotton in the 

 reflector. This result is rendered more important by 

 the fact that the sound reached the Mucking Light, a 

 distance of 13^ miles, against a light wind which was 

 blowing at the time. 



Most, if not all, of our ordinary sound-producers 

 send forth waves which are not of uniform intensity 

 throughout. A trumpet is loudest in the direction of 

 its axis. The same is true of a gun. A bell, with its 

 mouth pointed upwards or downwards, sends forth waves 

 which are far denser in the horizontal plane passing 

 through the bell than at an angular distance of 90 from 

 that plane. The oldest bellhangers must have been 

 aware of the fact that the sides of the bell, and not its 

 mouth, emitted the strongest sound, their practice being 

 probably determined by this knowledge. Our slabs of 

 gun-cotton also emit waves of different densities in differ- 

 ent parts. It has occurred in the experiments atShoebury- 

 ness thatwhen the broad side of a slab was turned towards 

 the suspending wire of a second slab six feet distant, the 

 wire was cut by the explosion, while when the edge of 

 the slab was turned to the wire this never occurred. 



