420 WRITINGS OF JOSEPH HENRY. [1874 



much precision, so that we are enabled in most cases to 

 explain, predict, and control the phenomena exhibited under 

 given conditions. But in the case of loud sounds and those 

 which are propagated to a great distance, (such as are to be 

 be employed as fog-signals,) considerable obscurity still exists. 

 As an illustration of this I may mention the frequent occur- 

 rence of apparently abnormal phenomena. General G. K. 

 Warren informs me that at the battle of Seven Pines, in 

 June, 1862, near Richmond, General Johnston, of the Confed- 

 erate army, was within three miles of the scene of action with 

 a force intended to attack the flank of the Northern forces, 

 and although he listened attentively for the sound of the 

 commencement of the engagement, the battle — which was a 

 severe one lasting about three hours, ended without his hav- 

 ing heard a single gun. (See Johnston's report.) Another 

 case of a similar kind occurred to General McClellan at the 

 battle of Gaines' Mills, June 27, 1862, also near Richmond. 

 Although a sharp engagement was progressing within three 

 or four miles for four or five hours, the General and his staff 

 were unaware of its occurrence, and when their attention 

 was called to some feeble sound, they had no idea that it was 

 from anything more than a skirmish of little importance. 

 (See Report of the Committee on the Conduct of the War.) 

 A third and perhaps still more remarkable instance is given 

 in a skirmish between a part of the Second Corps under 

 General Warren and a force of the enemy. In this case the 

 sound of the firing was heard more distinctly at General 

 Meade's headquarters than it was at the headquarters of the 

 Second Corps itself, although the latter was about midway 

 between the former and the point of conflict. The sound 

 appeared so near General Meade's camp that the impres- 

 sion was made that the enemy had advanced between it and 

 General Warren's command. In fact, so many instances 

 occurred of wrong impressions as to direction and distance 

 derived from the sound of guns, that little reliance came to 

 be placed on these indications. 



In the report of a series of experiments made under the 

 direction of the Light-House Board by General J. C. Duane, of 



