506 RESEARCHES IN SOUND. 



iites after lcavin,2:, but not beard at IG minutes; we may tberefore assume 

 tbat it became inaudible at 15 minutes. And witbin a minute of tbe 

 same time, by a mistake of tbe signal, tbe otber ceased to advance, and 

 commenced to come back ; tbe sound from it, bowcver, was very distinct, 

 wbile at tbe same moment tbe sound from tbe otber was inaudible. On 

 account of tbe mistake mentioned, tbe relative distance at wbicb tbe 

 sounds from tbe two vessels migbt bave become inaudible cannot be 

 accurately given; but tbe fact observed, tbat tbe sound wbicb came 

 witb tbe wind was mucli more audible tban tbe otber, is in conformity 

 witb tbe generally observed fact tbat sound is beard fartber witb tbe 

 wind tban against it. In tbe mean time tbe velocity of tbe wind bad 

 sunk to 1^ miles per bour. 



Next, tbe vessels, leaving at 11:55 A. m. cbanged positions ; tbe Cac- 

 tus, under Captain Davis, steamed west, directly in tbe direction from 

 wbicb tbe wind came, wbile tbe INIistletoe, under General Woodrufl", 

 steamed east, directly before tbe wind. Tbe result of tbis trial was well 

 marked in all respects ; tbe sound of tbe Mistletoe was lost in 9 minutes, 

 wbicb, from tbe speed of tbe steamer, was estimated at about lA miles, 

 wbile tbe sound of tbe Cactus was beard distinctly for 30 minutes, or 

 at an estimated distance of 5 miles. Tbe wind at tbe middle of tbis 

 trial bad sunk to 0.12 mile per bour, or nearly to a calm. Tbe result of 

 tbis trial was somewbat abnormal, for tbougb tbe wind bad sunk nearly 

 to a calm, tbe sound was still beard tbree times as far in tbe direction of 

 tbe sligbt wind as against it. 



After a lai)se of an bour and a balf a tbird trial was made ; in tbe 

 mean time tbe wind bad cbanged witbin two points of an exactly 

 opposite direction, blowing, from tbe indications of tbe anemometer, at 

 tbe rate of ten and one-balf miles per bour. 



Tbe Cactus again steamed in tbe eye of tbe wind, wbicb was now 

 bowever from nearly an opposite point of tbe compass, wbile tbe otber 

 vessel steamed in an opposite direction. Tbe sound of tbe Cactus was 

 lost at tbe end of twenty-seven minutes, witb tbe wind, or at a distance 

 of four and a balf miles. 



Tbe sound of tbe IMistletoe was lost at tbe end of tbirty minutes, or 

 at a distance of live miles, moving against a brisk wind tbeu blowing. 



Tbis result was entirely unexpected and mucb surprised every member 

 of tbe party, since it was confidently exj^ected tbat an increase in tbe 

 intensity of tbe wind of more tban ten miles per bour, and a cbange to 

 tbe opposite direction, would materially affect tbe audibility of tbe 

 sound, and give a large result in favor of tbe sound, wbicb moved in 

 tbe same direction witb tbe wind, but tbis was not tbe case. In tbe 

 course of all tbe observations in several years in wbicb investigations 

 bave been carried on under tbe direction of tbe cbairman of tbe board, 

 tbis is tbe only instance in wbicb be bad beard a sound at a greater dis- 

 tance against tbe wind tban witb it, altbougb, as before stated, a num- 



