1875] WKITINGS OF JOSEPH HENRY. 469 



wind, as has been asserted. In this case the ratio of the 

 latter to the former is as 11 to 6, or nearly double. 



The investigation of the relation of wind to the penetra- 

 tion of sound was renewed in a series of subsequent experi- 

 ments, the results of which are to be given in a succeeding 

 part of this report. 



It should be observed, in comparing Fig. 5 with the sub- 

 sequent figures representing the curve of audibility, that the 

 arrow representing the direction of the wind points in the 

 longest direction to the figure, whereas in other figures the 

 pointing is in the opposite direction. The difference arises 

 from the fact that in Fig. 5 the sound is supposed to radiate 

 from the centre, C, while in the others the sound converges to 

 the centre as a point of observation. The foregoing diagram 

 and all that follow in this report were plotted by Mr. Edward 

 Woodruff, assistant superintendent of construction of the 

 third light-house district. 



Experiments at Little Gull Island, September, 1875. 



The next series of experiments made during this season was 

 at Little Gull Island, at the east end of Long Island Sound. 

 This location was chosen on account of its convenience of 

 approach from the harbor of New London, seven miles dis- 

 tant, at which the light-house steamers of the third district 

 usually remain when not engaged in active service, and also 

 because there is a light-house on the island furnished with 

 two sirens of the second order, and an extent of water on 

 every side which would allow the vessels used in the experi- 

 ments to proceed from the island as a centre to a consider- 

 able distance in every direction. The island itself is a small 

 protuberance above the water, merely sufficient in area to 

 support a raised circular platform of about 100 feet in 

 diameter, on wiiich the light-house and other buildings are 

 erected. The following sketch (Fig. 6) will give an idea of 

 the position of Little Gull Island relative to the mainland 

 and the islands in the vicinity. 



From this it will be seen that the position was not the 

 most favorable for a stable condition of the atmosphere. As 



