RESEARCHES IN SOUND. 545 



greater on the semi-circumfereuce 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 dif- 

 ferent sizes, the result being that a whistle of less than ten inches diam- 

 eter does not give a sound which can be heard as far as one of the latter 

 size, although it appears to the ear near by equally loud. 



There is a difference between the quantity of sound and the loudness. 

 Two sounds may be equally loud when heard near by, yet differ very 

 nuich in regard to their being heard at a distance, the loudness depend- 

 ing upon the intensity of sound or on the amplitude of vibration of the 

 sounding body, while the quantity of sound depends on the extent of 

 the vibrating surface. 



The size of the whistle must be limited by the quantity of air ejected 

 at each oscillation of the buoy. The fact that the ten-inch whistle gives 

 a sound which can be heard farther than one of eight inches appears to 

 have a bearing on the question (the actuating force being the same) of 

 the united effect of two sounds of the same quantity and pitch, since 

 the sound fi'om several parts of the circumference of the larger whistle 

 may be considered as a union of several sounds of less quantity. 



After these observations on the automatic buoy we proceeded along the 

 coast to AVhite Head, at the entrance of Penobscot Bay, a distance of 

 sixty miles, which we reached at about twelve o'clock at night, and cast 

 anchor in Seal Harbor, near the White Head light-house. 



Our first operation next morning was the examination of an automatic 

 fog-bell, invented by Mr. Close, and which has been erected by a special 

 appropriation of Congress. It is very simple in conception, and would 

 do good service in southern latitudes, where it would not be affected by 

 the ice. It consists of an upright shaft thirty-two feet long, fastened to 

 the rock beneath the water, and kept in a vertical position by a series 

 of iron rods serving as braces. Around this shaft is a hollow metallic 

 float, having sufficient buoyancy by the motion of the waves to elevate 

 a vertical rod having at the upper end a rack gearing into a ratchet- 

 wheel. By means of projecting pins on the surface of the wheel the 

 hammer of the bell is elevated and the bell sounde<l at each descent of 

 the float. This arrangement is the most simple and eflicieut of any of 

 the kind of which we have any knowledge. 



The objection to it is its liability to be deranged by the action of ice 

 and the rusting of the i)arts from exposure to the weiither. 



Our next operation at this place was the examination of the remark- 

 able abnormal phenomenon, which was the principal object of our 

 excursion. It has been frequentlj^ observed by the captains of the 

 steamers plying between Boston and New Brunswick, and has also been 

 noticed on two different occasions by officers of the light-house estab- 

 lishment. The phenomenon, as reported by these authorities, consists 

 S. Mis. 59 35 



