1874] WRITINGS OF JOSEPH HENRY. 439 



eral Woodruff, and as the vessel steamed against the wind, 

 the sound came to the observers on the stationary vessel with 

 the wind; the other members of the party remained on the 

 Putnam, at anchor at the point before mentioned, off the 

 Hook, Major Hains having charge of the signals. The sound 

 of the first of the vessels was heard faintly at 14 minutes 

 after leaving, but not heard at 16 minutes; we may there- 

 fore assume that it became inaudible at 15 minutes. And 

 within a minute of the same time, — by a mistake of the sig- 

 nal, the other ceased to advance, and commenced to come 

 back ; the sound from it however was very distinct, while at 

 the same moment the sound from the other was inaudible. 

 On account of the mistake mentioned, the relative distance 

 at which the sounds from the two vessels might have become 

 inaudible cannot be accurately given ; but the fact observed, 

 that the sound which came with the wind was much more 

 audible than the other, is in conformity with the generally 

 observed fact that sound is heard farther with the wind than 

 against it. In the meantime the velocity of the wind had 

 sunk to 1| miles per hour. 



2d trial. — Next the vessels leaving at 11:55 a. m. changed 

 positions; the Cactus, under Captain Davis, steamed west, di- 

 rectly in the direction from which the wind came, while the 

 Mistletoe, under General Woodruff, steamed east, directly be- 

 fore the wind. The result of this trial was well marked in all 

 respects; the sound of the Mistletoe was lost in 9 minutes, 

 which, from the speed of the steamer, was estimated at about 

 1^ miles, while the sound of the Cactus was heard distinctly 

 for 30 minutes, or at an estimated distance of 5 miles. The 

 wind at the middle of this trial had sunk to 0*42 mile per 

 hour, or nearly to a calm. The result of this trial was some- 

 what abnormal, for though the wind had sunk nearly to a 

 calm, the sound was still heard three times as far in the 

 direction of the slight wind as against it. 



Sd trial. — After a lapse of an hour and a half a third trial 

 was made; the wind had changed within two points of an 

 exactly opposite direction, blowing (from the indications of 

 the anemometer) at the rate of 10| miles per hour. 



