7 o2 THE POPULAR SCIENCE MONTHLY. 



of the weather the howitzer firing a 3-lb. charge commands a larger 

 range than the whistles, trumpets, or siren. This was the case, for 

 example, on the particular day, October 17th, when the ranges of all 

 the sounds reached their maximum. 



On many other days, however, the inferiority of the gun to the 

 siren was demonstrated in the clearest manner. The gun-puffs were 

 seen with the utmost distinctness at the Foreland, but no sound was 

 heard, the note of the siren at the same time reaching us with distinct 

 and considerable power. 



The disadvantages of the gun are these : 



a. The duration of the sound is so short that, unless the observer 

 is prepared beforehand, the sound, through lack of attention rather 

 than through its own powerlessness, is liable to be unheard. 



b. Its liability to be quenched by a local sound is so great, that it * 

 is sometimes obliterated by a puff of wind taking possession of the 

 ears at the time of its arrival. This point was alluded to by Arago, 

 in his report on the celebrated experiments of 1822. By such a puff 

 a momentary gap is produced in the case of a continuous sound, but 

 not entire extinction. 



c. Its liability to be quenched or deflected by an opposing wind, so 

 as to be practically useless at a very short distance to windward, is 

 very remarkable. A case has been cited in which the gun failed to 

 be heard against a violent wind at a distance of 550 yards from the 

 place of firing, the sound of the siren at the same time reaching us 

 with great intensity. 



Still, notwithstanding these drawbacks, I think the gun is entitled 

 to rank as a first-class signal. I have had occasion myself to observe 

 its extreme utility at Holyhead and the Kish light-vessel near Kings- 

 town. The commanders of the Holyhead boats, moreover, are unani- 

 mous in their commendation of the gun. An important addition in 

 its favor is the fact that in fog the flash or glare often comes to the 

 aid of the sound ; on this point the evidence is quite conclusive. 



There may be cases in which the combination of the gun with one 

 of the other signals may be desirable. Where it is wished to confer 

 an unmistakable individuality on a fog-signal station, such a combi- 

 nation might with advantage be resorted to. 



If the gun be retained as one form of fog-signal (and I should be 

 sorry at present to recommend its total abolition), it ought to be of 

 the most suitable description. Our experiments prove the sound of 

 the gun to be dependent on its shape ; but we do not know tlrat we 

 have employed the best shape. This suggests the desirability of con- 

 structing a gun with special reference to the production of sound. 1 



An absolutely uniform superiority on all days cannot be conceded to 

 any one of the instruments subjected to examination ; still, our observa- 



1 The Elder Brethren have already had plans of a new signal-gun laid before them by 

 the constructors of the War Department. 



