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THE CHRISTIAN PHILOSOPHER, 



Acoustic Tunnels. By means of the inven 

 tions just now adverted to, when brought toper- 

 lection, mankind may be enabled to transport 

 themselves to every region of the globe, with a 

 much greater degree of rapidity that has hitherto 

 been attained. By the help of the microscope, 

 we are enabled to contemplate the invisible 

 worlds of life, and by the telescope we can pe 

 netrate intc regions far beyond the range of the 

 unassisted eye. By the arts of writing and 

 printing, we can communicate our sentiments, 

 after a certain lapse of time, to every quarter of 

 the world. In the progress of human knowledge 

 and improvement, it would obviously be of con 

 siderable importance, could we extend the range 

 of the human voice, and communicate intelligence 

 to the distance of a thousand miles, in the course 

 of two or three hours ; or could we hold an 

 occasional conversation with a friend at the dis 

 tance of 20 or 30 miles. From the experiments 

 which have been lately made, in reference to the 

 conveyance of sound, we have some reason to 

 believe, that such objects may not be altogether 

 unattainable. It has been long known, that 

 wood is a good conductor of sound. If a watch 

 be laid on the end of a long beam of timber, its 

 beating will be distinctly heard, on applying the 

 ear to the other end, though it could not be heard 

 at the same distance through the air. In &quot; Ni 

 cholson s Philosophical Journal&quot; for February, 

 1803, Mr. E. Walker describes a simple appa 

 ratus, connected with a speaking trumpet, by 

 means of which, at the distance of 17$ feet, he 

 held a conversation with another in whispers, too 

 low to be heard through the air at that distance. 

 When the ear was placed in a certain position, 

 the words were heard as if they had been spoken 

 by an invisible being within the trumpet. And 

 what rendered the deception still more pleasing, 

 the words were more distinct, softer, and more 

 musical, than if they had been spoken through 

 the air. 



About the year 1750, a merchant of Cleves, 

 named Jorisen, who had become almost totally 

 deaf, sitting one day near a harpsichord, while 

 some one was playing, and having a tobacco- 

 pipe in his mouth, the bowl of which rested acci 

 dentally against the body of the instrument, he 

 was agreeably and unexpectedly surprised to 

 hear all the notes in the most distinct manner. 

 By a little reflection and practice, he again ob- 



and they rise into the atmosphere, on the same prin 

 ciple as a piece of cork ascends from the bottom of 

 a pail of water. The aerial travellers are seated in 

 a basket below the balloon, which is attached to it 

 by means of cords. The parachute is an invention, 

 by which the voyager, in cases of alarm, may be 

 enabled to desert his balloon in mid-air, and descend, 

 without injury, to the ground. They resemble an 

 umbrella, but are of far greater extent. With one 

 jf these contrivances, twenty-three feet in diameter, 

 M. Garnerin, having detached himself from h.s t-a. 

 oon, descended from a height of more than 4000 feet, 

 and Ian led without shock or accident. 



tained the use of this valuable sense ; for he soo 

 learned, by means of a piece of hard wood, one 

 end of which he placed against his teeth, while 

 another person placed the other end on his teeth, 

 to keep up a conversation, and to be able to un 

 derstand the least whisper. In this way, two 

 persons who have stopped their ears may con 

 verse with each other, when they hold a long 

 stick or a series of sticks between their teeth, or 

 rest their teeth against them. The effect is the 

 same, if the person who speaks rests the stick 

 against his throat, or his breast, or when one 

 rests the stick which he holds in his teeth against 

 some vessel into which the other speaks ; and 

 the effect will be greater, the more the vessel is 

 capable of tremulous motion. These experi 

 ments demonstrate the facility with which the 

 softest whispers may be transmitted. Water 

 also is found to be a good conductor of sound. 

 Dr. Franklin assures us, that he has heard under 

 water, at the distance of half a mile, the sound 

 of two stones struck against each other. It has 

 been also observed, that the velocity of sound is 

 much greater in solid bodies, than in the air. 

 By a series of experiments, instituted for the 

 purpose of determining this point, Mr. Chladni 

 found that the velocity of sound, in certain solid 

 bodies, is 16 or 17 times as great as in air. 



But what has a more particular bearing on the 

 object hinted at above, is, the experiments lately 

 made by M. Biot, &quot; on the transmission of sound 

 through solid bodies, and through air, in very 

 long tubes.&quot; These experiments were made by 

 means of long cylindrical pipes, which were 

 constructing for conduits and aqueducts, to em 

 bellish the city of Paris. With regard to the 

 velocity of sound, it was ascertained that &quot; its 

 transmission through cast iron is 10$ times as 

 quick as through air.&quot; The pipes by which he 

 wished to ascertain at what distance sounds are 

 audible, were 1,039 yards, or nearly five furlongs, 

 in length. M. Biot was stationed at the one end 

 of this series of pipes, and Mr. Martin, a gen 

 tleman who assisted in the experiments, at the 

 other. They heard the iowest voice, so as per 

 fectly to distinguish the words, and to keep up 

 a conversation on all the subjects of the experi 

 ments. &quot; I wished,&quot; says M. Biot, &quot; to deter 

 mine the point at which the human voice ceases 

 to be audible, but could not accomplish it : words 

 spoken as low as when we whisper a secret in 

 another s ear, were heard and understood ; so that 

 not to be heard, there was but one resource, that 

 of not speaking at all. This mode of conversing 

 with an invisible neighbour is so singular, that 

 we cannot help being surprised, even though 

 acquainted with the cause. Between a question 

 and answer, the interval was not greater thar 

 was necessary for the transmission of sound. 

 For Mr. Martin and me, at the distance of 1,039 

 yards, the time was about 5j seconds.&quot; Re- 

 ports of a pisto, fired at one end, occasioned 



