478 RESEARCHES IN SOUND. 



A similar result cannot be expected with the use of the whistle or 

 the trumpet, since in the Ibrmer the stiffness of the aerial reed depends 

 upon its density, which will be in proportion to the pressure in the 

 boiler, and in the case of the latter no sound can be produced on^ the 

 one hand unless the pressure be sufficient to overcome the resistance of 

 the reed, and on the other the sound must cease when the pressure is 

 so great as to prevent the recoil of the reed. 



5. An experiment was made to determine the effect of a small whistle 

 inserted i-jro the side of a trumpet near the small end. The whistle 

 being souiuled before and after it was placed in the trumpet, the result 

 was as follows: The penetrating powers were in the ratio of 40: 51, 

 •while the tone was considerably modified. From this experiment it 

 appears that a whistle may be used to actuate a trumpet or to exercise 

 the functions of a reed. In order however to get the best results, it 

 would be necessary that the trumpet and whistle should be in unison, 

 but it may be doubted however whether an increase of effect, with a 

 given amount of power, would result from using such an arrangement; 

 it might nevertheless be of advantage in certain cases to direct the 

 sound of a locomotive in a definite direction, and to use a smaller 

 whistle, especially in cities, in which the locomotive passes through long 

 streets; perhai^s in this case the sound migiit be less disagreeable than 

 that of the naked whistle, which sends its sound-waves laterally with 

 as much force as in the direction of the motion of the engine. 



6. General Poe called attention to the sound produced by the paddle- 

 wheels of a steamer in the offing at a distance estimated at four and a 

 half miles. The sound was quite distinct when the ears were brought 

 near the surface of the beach. 



In this connection he stated that he had heard the api)roach of a 

 small steamer on the northern lakes when its hull was still below the 

 horizon, and was even enabled to designate the particular vessel from 

 among others by the peculiarity of the sound. 



The sound in the case of the steamer is made at the surface of the 

 water, and it might be worth the trouble to try experiments as to the 

 transmission of sound under this condition, and the collection of it by 

 means of ear-trumpets, the mouths of which are near the water, the 

 sound being conveyed through tubes to the ears of the pilot. In order 

 however to determine in this case the direction of the source of sound, 

 two trumpets would be necessary, one connected with each ear, since 

 we judge of the direction of a sound by its simultaneous effects on the 

 two auditory nerves. This suggestion, as well as many others which 

 have occurred in the course of these researches, is worthy of special in- 

 vestigation. 



7. A series of experiments was made to compare trumpets of different 

 materials and forms having the same length and transverse areas, all 

 blown at a pressure of 9| pounds. 



