40 



noise of the waves greatly interfering, in both, with the powers of 

 hearing. In the trumpet-shaped apparatus, the ringing of the metal, 

 from the blow of the waves, was partly guarded against by a wooden 

 casing; but, as it was open at both ends, the oscillation of the water, 

 in the tube was found to be a still greater inconvenience, so that the 

 sound of the bell was better heard with the cylindrical tube. At the 

 distance of a quarter of a mile this sound was a sharp tap, about 

 the loudness of that occasioned by 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 

 apparatus, 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 contact with the surface of the water. In these experiments 

 the cone was placed at right angles to the stem, and the mouth di- 

 rected toward the sound. The distances were measured by the in- 

 terval elapsed between the observed flash and report of a pistol. At 

 the distance of 1400 feet, the conical instrument was found consider- 

 ably superior to the cylindrical, and at greater distances the supe- 

 riority 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 appeared that the blow of a watchmaker's ham- 

 mer 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 undertaken ; that is, to ascertain whether an echo would be re- 

 turned, through water, from the bottom of the sea. Some difficulties 

 were at first presented in exploding the gun under water, but these 

 were at length overcome. The hearing-tube was ballasted so as to 

 sink vertically in the water. The observers then went, with this in- 



