It is on account of this principle, that in long ranks of 

 soldiers where two bands of music are placed at a con- 

 siderable interval from each other, it is impossible for 

 the two bands to keep time with each other. They may 

 indeed play together, but each soldier will hear the 

 nearest sounds quickest, and thus they will seem to be 

 out of time. It is often noticed too, that if from an emi- 

 nence we look upon a long column which is marching 

 to a band of music in front, the various ranks do not 

 step exactly together. Those in the rear are in each 

 step a little later than those before them. This produces 

 a sort of undulation in the whole column, which is diffi- 

 cult to describe but which all who have noticed it will 

 understand. Each rank steps, not when the sound is 

 made, but when in its progress down the column at the 

 rate of 1142 feet per second, it reaches their ears. 

 Those who are near the music hear it as soon as it is 

 produced, while the others must wait till sufficient time 

 shall have elapsed, for it to have passed through the air 

 to them. 



Should a commander stand at the distance of a fifth 

 of a mile from his army, and command them to fire, they 

 might all obey at the moment when the word of command 

 reaches them ; but the officer will hear the report of the 

 guns from those at the side nearest him first, then those 

 a little farther off, and so on to the most remote. Thus 

 though all might obey with equal alacrity, the sounds will 

 not, and cannot appear simultaneous, for the reports of the 

 distant guns must be delayed long enough for the com- 

 mand to pass from the officer to the men, and then for 

 the sound to return. All attempts therefore to make the 

 firing appear exactly simultaneous from a long line must 

 be in vain. 



5. Distances calculated by the velocity of Sound. 



The velocity of sound being thus once ascertained, it 

 is evidently easy to calculate with the assistance of this 

 knowledge, the distance of any object near which a loud 

 sound is produced, as a ship firing a gun at sea, or a 

 thunder cloud. 



VOL. i. NO. xiii. 29 



