1877] WRITINGS OF JOSEPH HENRY. 489 



that it can be permanently moored in deep water, and that 

 vessels can safely approach it within the nearest distance and 

 take perfect departure from it. 



The Light-House Board has adopted this buoy as one of 

 its permanent aids to navigation, and will in time introduce 

 it at all points where its presence will be of importance to 

 the navigator. In order to obtain reliable data as to the 

 operations of the automatic buoy. Commander Picking has 

 established a series of observations at all the stations in the 

 neighborhood of the buoys, giving the time of hearing it, 

 the direction of the wind, and the state of the sea ; from 

 which it appears that in the month of January, 1877, one of 

 these buoys was heard every day at a station one and one- 

 eighth miles distant; every day but two, at a station two and 

 one-quarter miles distant ; fourteen times at a station seven 

 and one-half miles distant, and four times at a station eight 

 and one-half miles distant. It is heard by the pilots of the 

 New York and Boston steamers at distances of from one-fifth 

 to five miles, and has frequently been heard by the inspector 

 of the first light-house district at a distance of nine miles, and 

 even (under the most favorable circumstances) fifteen miles. 



We sailed around the buoy and observed the difference in 

 the intensity of sound relatively to the direction of the wind, 

 which was at the time a fresh breeze of from twelve to fifteen 

 miles per hour from the westward ; — the greatest intensity 

 being apparently at points forty-five degrees on either side 

 of the axis of the wind. The effect however was not very 

 definitely marked, though the sound on the whole appeared 

 to be greater on the semi-circumference of the circle to the 

 leeward; but the velocity of the wind was so great that the 

 noise produced by it on the rigging of the vessel prevented 

 the effects from being definitely observed. 



Experiments have been made with this buoy carrying 

 whistles of different sizes, the result being that a whistle of 

 less than ten inches diameter does not give a sound which 

 can be heard as far as one of the latter size, although when 

 near by, it appears to the ear equally loud. 



There is a difference between the quantity of sound and 



