782 



PLATE XXV. 



rig. 340. A scries of waves or pulses of sound, 

 diverging frem one of the foci of an ellipsis, and re- 

 flected towards the other. P. 375. 



rig. 341. Waves diverging from a point near the 

 centre of a circle, and converging after reflection to 

 a point at an equal distance on the other side of the 

 centre. P. 375. 



rig. 342. A section of a speaking trumpet and of a 

 hearing trumpet: the lines representing the direction 

 of tlie sound before and after its reflections. P. 375. 



Fig. 343. A string impelled by the bow of a violin, 

 and lightly touched at tl>e same time at a point one 

 third of its length from the end : the small pieces of 

 paper fly ofl' from the middle of tl>e vibrating portions, 

 while the pi^ce situated at the remaining point of 

 division retains its situation. P. 383. 



Fi". 344. A vibration compounded with another 

 smaller vibration, three times as frequent, in a trans- 

 verse direction, the separate vibrations being such 

 that tl'.e points may be always opposite to a point 

 moving uniformly in a circle. Thus the vibrations in 

 the hnes AB and AC compose the complicated 

 figure D E. P. 384. 



Fi" 345. A specimen of the manner in which the 

 -vibrations of a string are usually performed when it is 

 struck with a bow. P. 384. 



Fig. 346. Specimens of the simplest manner iij 

 which sand is collected into lines, on a plate of glass 

 or metal, which is made to sound i)y means of the bow 

 4)f a violin. P. 385. 



Fig. 847. A round plate, performing some of its 

 most complicated vibrations, the lines of division 

 being indicated by the place of the sand. From 

 Chladni. P. 385. 



Fig. 348. A square plate divided into a diversity 

 of vibrating portions. From Chladni. P. 385. 



Fig. 34!>. The small bones of the left ear, nearly 

 three times the natural size, supposed to be seen 

 through tUe membrane of the tympanum, by looking 

 directly into ilie auditory canal. A B is the membrane 

 of the tympanum, C the hammer, D the anvil, E its 

 attachment to the surrounding bone, F the stirrup, G 

 the round aperture in the bone leading to the cochlea. 

 P. 388. 



Fig. 350. A view of the vestibule of the left ear, 

 with the semicircular canals and the cochlea, seen 

 with the eye a little more depressed than by looking 

 ktraight tlirough the canal, and exactly in the direc- 



tion of the stirrup. ABC is the vestibule, imme< 

 diately behind the oval aperture, which is covered by 

 the basis of the stirrup, D are the canals, E the 

 cochlea, the upper spire terminating in the vestibule, 

 the lower in the round aperture at B. The projec- 

 tion of the membrane of the tympanum is marked by 

 an oval line. P. 388. 



Fig. 351. The structure of the left ear, seen from 

 above, the upper part of the canal being supposed to 

 be removed. A is the auditory canal, B the membrane 

 of the tympanum, C the hammer, D the anvil, E the 

 stirrup; F the place of the canals, which are higher 

 than the parts represented, G the place of the cochlea, 

 H the round aperture. P. 388. 



Fig. 352. A,B, C, a representation of the joint 

 effect of two equal vibrations variously combined, the 

 middle line being always half way between the two 

 outer ones, and showing the compound vibration re- 

 duced to half its real extent: D shows the mode of 

 finding the joint efliect of vibrations, by cutting a sur- 

 face into sliders, which are retained in their places 

 by a screw. P. 390. 



Fig. 353. The uppermost and lowermost curves re- 

 present a series of vibrations, of which 12 occupy any 

 given period of time : the third and sixth lines two 

 series of which 15 and 16 occupy respectively the 

 same time: -the joint eflfcct of each pair is shown by 

 the dotted curves which are interposed between them, 

 the middle one representing the effect denominated 

 a beat. P. 391. 



Fi". 354. The proportional lengths of a chord or 

 pipe, constituting the different notes of the simple dia- 

 tonic scale, with their mutual relations, shown by their 

 divisions into aliquot parts. P. 393. 



Fi". 355. A good practical mode of temperament; 

 making all the fifths and the third in the first division 

 perfect concords; the three remaining fiULs equally 

 imperfect. P. 396. 



Fig. 356. Tlie trumpet Marigni, with its bridge, 

 which is suppoited by the string AB nearly in contact 

 with the sounding board; this string being either 

 stretched by a pin at B, or by a cross string B C. Jte 

 places, at which the string is to be touched, may be 

 marketl by frets fixed un<^erthc*h, as they are here 

 shown by points. At D, tlie scale of this instrument 

 is exhibitcrl, resembling that of the trumpet and the 

 French horn. P. 399. 



