440 WRITINGS OF JOSEPH HENRY. [1874 



The Cactus again steamed in the eye of the wind, which 

 was now however from nearly an opposite point, while the 

 other vessel steamed in an opposite direction. The sound of 

 the Cactus was lost (with the wind) at the end of twenty- 

 seven minutes, or at a distance of four and a half miles. 



The sound of the Mistletoe (moving against a brisk wind 

 then blowing) was lost at the end of thirty minutes, or at a 

 distance of five miles. 



This result was entirely unexpected and much surprised 

 every member of the party, since it was confidently expected 

 that an increase in the intensity of the wind of more tlian 

 ten miles per hour, and a change to the opposite direction, 

 would materially affect the audibility of the sound, and give 

 a large result in favor of the sound that moved in the 

 same direction with the wind; but this was not the case. In 

 the course of all the observations in several years in which 

 investigations have been carried on under the direction of 

 the chairman of the board, this is the only instance in which 

 he had heard a sound at a greater distance against the wind 

 than with it; although (as before stated) a number of cases 

 have been reported by other observers in which (under pecu- 

 liar conditions of the weather) this phenomenon has been 

 obsecved. 



To briefly recapitulate the results, we have in this case 

 three instances in succession in which a sound was heard 

 farther from the west than from the east, although in the 

 meantime the wind had changed to nearly an opposite direc- 

 tion. Had these results been deduced from the first obser. 

 vatioiLS made on the influence of wind on sound, or in other 

 words without previous experience, the conclusion would 

 have been definitely reached that something else than wind 

 affected the conveyance of sound, and this conclusion would 

 have been correct if the suggestion had been confined to the 

 wind at the surface; but from previous observations and 

 theoretical conclusions, the observed phenomena are readily 

 accounted for by supposing that during the whole time of 

 observation the wind was blowing from the west in the 

 higher part of the aerial current, and that the calm and 



