466 EESEAECHES IN SOUND. 



distinctive character of its tone it lias, in our opinion, an advantage over 

 a single wliistle expending an eqnal quantity of steam. 



The fact that the vibration of the metal of the bell had no practical 

 effect on the penetrating power of the sound was proved quite conclu- 

 sively by winding tightly around each bell, over its whole length, a thick 

 cord, which would effectually stop all vibration. The penetration of the 

 sound produced under this condition was the same as that with the bells 

 free. It is true, the latter produces a difference in the quality of the 

 tone, such as that which is observed in a brass instrument and that of 

 one of wood or ivory. The inventor was not aware that the sound pro- 

 duced was from the resonance of the air within the bell, and not from 

 the metal of the bell itself, and had obtained a patent, not only for the 

 invention of the double whistle, but also for the special comx)ound of 

 metal of which it was composed. 



Another ajiparatus proposed to be used as a fog-signal was presented 

 for examination by the Marine Signal Company, of Wallingford, Conn. 

 It consisted of a curved tube of copper nearly in the form of the letter 

 C, and was supported on an axis passing through the center of the 

 figure. An ordinary bell- whistle was attached to each extremity of the 

 tube, the instrument being placed in a vertical jiosition and partially 

 filled with water, then made to oscillate on its center of support. By 

 this means the air was drawn in at one end and forced out through the 

 whistle at the other. The motion being reversed the air was drawn in 

 at the end through which it had just made its exit and forced out through 

 the whistle at the other. By rocking the instrument, either by hand or 

 by the motion of the vessel, a continued sound could be i)roduced. The 

 motive-power in the former case was muscular energy, and the experi- 

 ments which were made at this time, as well as all that have been made 

 subsequently, conclusively prove that the penetrating power of the 

 sound for practical use as a fog-signal depends upon the intensity of the 

 motive-energy employed. No instrument operated through levers and 

 pumps by hand-power is sufficient for the purpose. 



One of these instruments with two 4-inch whistles gave a sound, as 

 indicated by the artificial ear, the power of w^hich was about one- tenth 

 of that of a steam-trumpet. It was sui)posed however that this in- 

 strument would be applicable for light-ships ; and that if extended en- 

 tirely across the vessel, and armed with whistles of large size, it would 

 be operated by the rolling of the vessel, and thus serve to give warning 

 in time of thick weather. But as it frequently happens that fog exists 

 during a calm, this invention could not be relied upon to give warning 

 in all cases of danger. Besides this, the ordinary roll of a ship is not 

 sufficient to produce a hydrostatic pressure of more than five or six 

 pounds to the square inch, which is insufficient to give an effective 

 sound. It has however been proposed to increase the jjower by using 

 quicksilver instead of water; but, besides the first cost of this material, 

 and the constant loss by leakage and oxidation, the tendency to affect 



