39 



Dr. Patterson read a paper by Professor Charles Bonny- 

 castle, of the University of Virginia, containing "Notes of Ex- 

 periments, made August 22d to 25th, 1838, with the view of 

 determining the Depth of the Sea by the Echo." 



This paper, which was not offered for publication in the Society's 

 Transactions, states that the generally received notions in regard to 

 the intensity of sound in water, and the distance to which it is con- 

 veyed, had suggested to Mr.- Bonnycastle, some years ago, the idea 

 that an audible echo might be returned from the bottom of the sea, 

 and the depth be thus ascertained from the known velocity of sound 

 in water. The probability of this view was deemed at least sufficient 

 to justify an experiment; and accordingly the Navy Commissioners 

 authorized the construction of the necessary apparatus, and Captain 

 Gedney, of the U. S. Brig Washington, attached to the coast survey, 

 volunteered his services and the use of his vessel, and authority to 

 this effect was liberally granted by the Secretary of the Treasury, 

 Mr. Woodbury. 



The apparatus, which is fully described in Mr. Bonnycastle's 

 paper, consisted, first, of a petard or chamber of cast iron, 2| inches 

 in diameter and 5 J inches long, with suitable arrangements for firing 

 gunpowder in it under water; secondly, of a tin tube, 8 feet long and 

 Ijj inches in diameter, terminated at one end by a conical trumpet- 

 mouth, of which the diameter of the base was 20 inches, and the 

 height of the axis 10 inches; thirdly, of a very sensible instrument 

 for measuring small intervals of time, made by J. Montandon of 

 Washington, and which was capable of indicating the sixtieth' part of 

 a second. Besides these, an apparatus for hearing was roughly 

 made on board the vessel, in imitation of that used by Colladon in 

 the Lake of Geneva, and consisted of a stove-pipe, 4^ inches in di- 

 ameter, closed at one end, and capable of being plunged four feet in 

 the water. The ship's bell was also unhung, and an arrangement 

 made for ringing it under water. 



On the 22d of August, the brig left New York, and in the evening 

 the experiments were commenced. In these, Mr. Bonnycastle was 

 assisted by the commander and officers of the vessel, and by Dr. 

 Robert M. Patterson, who. had been invited to make one of the party. 



In the first experiments, the bell was plunged about a fathom 

 under water and kept ringing, while the operation of the two hearing 

 instruments was tested at the distance of about a quarter of a mile. 

 Both instruments performed less perfectly than was expected; the 



