27S 



rO&OI& AOOC6TI08. 



[MUSICAL sot-NDH. 



rail ; and an ear, placed in any portion of it, will hear 

 tlii'm distinctly. If a concave reflector be to placed a* 

 to receive the rays of sound from a louroo at its focus, 

 and another reflector be to arranged at a considerable 

 distance from the first, but to that their foci shall be in 

 one straight linethen all the sound* proceeding from 

 the first reflector will be received on the face of the 

 second, and be again reflected to its focus. If tho ear 

 be placed at that spot, all the sounds proceeding from 

 the distant reflector will be distinctly heard, and yet 

 none will be audible at any place intermediate bet 

 the two foci Again, even if much noise be made on all 

 idea of the reflectors, still the sounds at the focus will 

 be readily distinguished, although they may have passed 

 through a considerable distance of intermediate air. 

 A very similar result is produced when heat is reflected, 

 as has been shown under that section.* 



On the principle of reflection, speaking-tubes are con- 

 st nictcd, which simply consist of pipes having an even 

 internal surface. The sound is reflected from side to 

 side until it reaches tho other extremity of the tube. 

 These arrangements are largely employed in the ware- 

 houses, A'c. , of our cities, and are a great saving of time 

 and trouble. An amusing effect may be produced by a 

 modification of the speaking-tube. Two tubes may be 

 inserted in a head of wood, or plaster one communi- 

 cating with the mouth, and the other with tho ear of the 

 figure, in the manner illustrated in the following en- 

 graving. A tube is carried into an adjacent room, and, 



Pg. . 



of course, a person must there listen and reply to any 

 inquiries whi.spered in tho ear of the figure. The reply 

 is received by listening at the mouth of the bust. This 

 resembles what has been termed the "invisible lady," 

 which, however, was first introduced to the public as an 

 acoustic toy, in the following form. 



Fig. 9. 



No. 1. No. J. 



No. I, Fig. 9, represents the apparatus in ita general 

 appearance. It consists of a wooden frame, a a, sup- 

 ported on four pillars, from one of which a tube passes 

 (as in our last illustration) to an adjacent room ; c is a 

 copper ball from which the tube proceeds ; and 6666 

 arc four openings in tho side of the ball These are 

 shown in section, in No. 2. Tho mode of using tho 

 arrangement is precisely similar to that we have just 

 mentioned in connection with the preceding illustration. 



Set ante, p. 27 ; Fig. 6. 



MUSICAL SOUNDS. 



WE shall now call attention to some of the laws observed 

 in connection with tho production of musical sounds; 

 having already explained the general results obtained by 

 the vibration of the air, and the conduction and reflection 

 of those vibrations by means of suitable media and 

 surfaces. 



Of all the pleasures derived by our senses, those of 

 music are tho most refining and elevating. They appeal 

 alike to the mind and the sentiments ; at times, soothing 

 tho troubled spirit, and yet often rousing into action the 

 military ardour of the soldier. It is, indeed, surprising 

 to observe the extensive influence which musical sound* 

 exert, whether they are produced by instruments, or by 

 the voice of man or birds. The ancients were so im- 

 pressed with this, that, amongst all their leading allegories 

 and mythological fables, many relating to the power of 

 music are included. The well-known tale of Or] -hens, 

 who was said to have charmed the very stones ; and tliu in- 

 fluence ascribed to Apollo, the god of Music, over tho gods 

 and men are instances, out of many others^ of the kind. 

 We shall divide this portion of our subject into two 

 parts. The first will deal with musical sounds as produced 

 by instruments : and this will bo followed by an account 

 of the physiology of animal voice ; for which we are 

 indebted to Dr. Bushnan. It has already been remarked, 

 that all sounds are caused by vibrations, but that such 

 differ according to tho body from which they proceed. 

 Besides, the sounds so produced vary from each other in 

 tone, and other particulars, according to certain definite 

 laws, which we will now inquire into. 



If a piece of steel be tightly held at one extremity, and 

 then struck, it will, of course, vibrate, and, in so doing, 

 will produce sound. If tho length of the steel beyond 

 the part at which it is held be decreased, then such sounds 

 will become sharper. On the other hand, if the length 

 be increased, then the sounds produced are duller, and 

 deeper in tone. A very convenient way of trying thii 

 experiment is represented in 

 the annexed engraving; in 

 which o is an ordinary vice ; 6 

 a piece of steel ribbon ; and 

 c c are dotted lines, showing the 

 vibrations produced on the 

 steeL The steel extremity, 

 beyond tho top of the vice, can 

 be lengthened or shortened, 

 by passing it, more or less, 

 through its sides or cheeks, as 

 may be required for altering 

 the sound. 



In trying this experiment, the 

 iv:uler may, by a little care, 

 produce not only an apparently 

 extensive range of sounds, but, 

 in so doing, will notice, that at 

 certain intervals the same kind 

 of sound is reproduced; but 

 either sharper or lower, ac- 

 cording as the length of the string is decreased or 

 increased. Now, these similar notes, or sounds, arn 

 termed octaves; that is, a musical sound repeats itself 

 at every eighth set of vibrations, when such are produced 

 according to certain rules. But intermediate to the notes 

 forming the extremities of the octave, there are others 

 which, to some extent, harmonise with them : such are 

 termed thirds and fifths, owing to their relative position 

 with that of the first or last octave note. This may 

 readily be tried on a pianoforte, by placing the fingers on 

 two successive C's, and then striking the following E and 

 O. If tho three notes be then struck together, the effect 

 of their harmony will bo at once apparent. 



Another mode of trying tho effect of increasing or 

 lengthening a vibrating cord, is that of stretching ti 

 a piece of catgut between any two points. If this be 

 vibrated it will produce sound, as usual. If it bo halved 

 in its vibrating length, by placing tho finger on it and 



Fig. 10. 



b . 



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