On Peals of Thunder. 103 



vast extent of the flash, but that they were not throughout of 

 the same intensity. Different portions of the sonorous agita- 

 tion would reach the ear by means of the sonorous undula- 

 tions of the air ilie one after the other ^ and the effect of this 

 would be a prolongation of the sound. Such also would be 

 the experience of a person placed at the extremity of a long file 

 of soldiers who should fire their muskets at the same instant. 

 This individual would also hear an irregular sound, provided 

 the muskets were not loaded precisely alike in the different 

 parts of the line." Let us pursue this comparison of the file 

 of soldiers all discharging their muskets at the same moment^ 

 and we shall thus see how it may happen that flashes of light- 

 ning of similar lengths in appearance, nevertheless occasion such 

 different sounds and peals. Suppose first, to direct our ideas, 

 that the file is rectilinear, and that there is a yard's distance 

 between each soldier and his neighboui^ Let us, moreover, 

 stippose that the observer, placed at one of the extremities of 

 the line, is, for example, at a yard's distance from the first sol- 

 dier. The noise of the muskets of the 1st, 2d, 3d, lOOth, &c. 

 &c. soldier, would reach him the ^J^, j§^, yg^, \%% of a second, 

 &c. &c. after the discharge. If there were 368 soldiers in the 

 line, the sound would continue 1 second^ although, in reality, 

 all the pieces were fired simultaneously. Were there 736 sol- 

 diers, the sound would last for 2 seconds; if 1105, for 3 se- 

 conds; if 3680 for 10 seconds, and >so on, always propor- 

 tionably, in succession. 



The file of soldiers still continuing rectilinear, let us now 

 place the observer upon some point of a perpendicular drawn 

 from its centre. The report that would then first strike his 

 ear, would be that from the musket of the soldier in the middle 

 of the file, or, in other words, the point whence the perpendicu- 

 lar was drawn. There would then successively reach him, and 

 in couples, the reports of the muskets of each two soldiers 

 . placed symmetrically as to the centre of the line ; the rolling 

 noise would terminate by the report proceeding from the dis- 

 charge of the muskets situated at the two extremities. 



Let us now substitute a circular for a rect'dinear line, and 

 let us place the observer in the centre. In this position, the 

 distance of the observer from all the soldiers being the same 



