163 Miscellanies^ 



striking the back of a penknife against an iron wire : at the distance of a 

 mile the sound was no longer audible. 



In the second experiments, the mouth of the cone, in the trumpet ap- 

 paratus, was closed with a plate of thick tin, and both instruments were 

 protected by a parcelling of old canvas and rope-yarn, at the part in con- 

 tact with the surface of the water. In these experiments the cone was 

 placed at right angles to the stem, and the mouth directed toward the 

 sound. The distances were measured by the interval elapsed between 

 the observed flash and report of a pistol. At the distance of 1400 feet, 

 the conical instrument was found considerably superior to the cylindrical, 

 and at greater distances the superiority became so decided, that the latter 

 was abandoned in all subsequent experiments. At the distance of 5270 

 feet, the bell was heard with such distinctness as left no doubt that it 

 could have been heard half a mile further. 



The sounds are stated in the paper to have been less intense than those 

 in air, and seemed to be conveyed to less distances. The character of 

 the sound was also wholly changed, and, from other experiments, it ap- 

 peared that the blow of a watchmaker's hammer against a small bar of 

 iron gave the same sharp tick as a heavy blow against the large ship's 

 bell. It is well known that Franklin heard the sound of two stones 

 struck together under water at half a mile distance ; yet two of the boat's 

 crew, who plunged their heads below the water, when at a somewhat less 

 distance from the bell, were unable to hear its sound. 



On the 24th of August, the vessel having proceeded to the Gulf Stream, 

 experiments were made with the view for which the voyage was under- 

 taken ; that is, to ascertain whether an echo would be returned, through 

 water, from the bottom of the sea. Some difficulties were at first pre- 

 sented in exploding the gun under water, but these were at length over- 

 come. The hearing-tube was ballasted so as to sink vertically in the 

 water. The observers then went, with this instrument, to a distance of 

 about 150 yards from the vessel, and the petard was lowered over the 

 stern, about three fathoms under water, and fired. The sound of the 

 explosion, as heard by Mr. Bonnycastle, was two sharp distinct taps, at an 

 interval of about one third of a second. Two sounds, with the same in- 

 terval, were also clearly heard on board the brig; but the character of the 

 sounds was different, and each was accompanied by a slight shock. 

 Supposing the second sound to be the echo of the first from the bottom 

 of the sea, the depth should have been about 160 fathoms. 



To ascertain the real depth, the sounding was made by the ordinary 

 method, but with a lead of 75 pounds weight, and bottom was distinctly 

 felt at 550 fathoms, or five furlongs. The second sound could not, there- 

 fore, have been the echo of the first ; and this was proved, on the follow- 

 ing day, by repeating the experiment in four fathom water, when the 

 double sound was heard as before, and with the same interval. 



