xxviii DESCRIPTION OF PLATES. 



which are higher than the parts represented, G the place of the cochlea, H the round 

 aperture. P. 302. 



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 reduced to half its real extent : D shows 

 the mode of finding the joint effect of vibrations, by cutting a surface into sliders, 

 which are retained in their places by a screw. P. 305. 



Fig. 353. The uppermost and lowermost curves represent 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 effect of each pair is 

 shown by the dotted curves which are interposed between them, the middle one 

 representing the effect denominated a beat. P. 305, 306. 



Fig. 354. The proportional lengths of a chord or pipe, constituting the different 

 notes of the simple diatonic scale, with their mutual relations, shown by their divi- 

 sions into aliquot parts. P. 307. 



Fig. 355. A good practical mode of temperament ; making all the fifths and the 

 third in the first division perfect concords ; the three remaining fifths equally imper- 

 fect. P. 309. 



Fig. 356. The trumpet of Marigni, with its bridge, which is supported by the 

 string A B nearly in contact with the sounding board ; this string being either 

 stretched by a pin at B, or by a cross string B C. The places at which the string is 

 to be touched, may be marked by frets fixed under them, as they are here shown by 

 points. At D, the scale of this instrument is exhibited, resembling that of the 

 trumpet and the French horn. P. 312. 



PLATE XXVI. 



Fig. 357. The right half of the human larynx. A B C is the outline of the cricoid 

 cartilage, D E F G H of the thyreoid, and I K L of the arytaenoid cartilage ; M is 

 the epiglottis, N K the upper ligament of the glottis, O P the lower ligament, and 

 Q the trachea. P. 313. 



Fig. 358. A view of the ligaments of the glottis, seen from above, the larynx 

 being divided by a horizontal section a little above them. P. 313. 



Fig. 359. Sections of the pipes employed by Kratzenstein for producing the 

 sounds of the different vowels ; in general by means of a larynx resembling the 

 mouth piece of a reed organ pipe, but in the case of the vowel I by simple inflation 

 through the tube B. The pipe for U produces the sound O, except when it is very 

 nearly shut up. P. 313. 



Fig. 360. The vox humana organ pipe, with the mouth piece common to reed 

 pipes in general ; the lower part in contact with the tongue being nearly semicylin- 

 drical ; the tongue being adjusted to the proper pitch by means of a sliding wire, 

 which regulates the length of the part that is at liberty to vibrate. P. 314. 



Fig. 361. The mouth piece proposed by Kratzenstein, for imitating the human 

 voice, the tongue A passing freely in and out of the tube, which is more than half of 

 a cylinder, as is seen at B. P. 314. 



Fig. 362. The form of the regal organ pipe. P. 314. 



Fig. 363. A front view and section of the open diapason organ pipe of metal. It 

 is tuned by opening or contracting the upper orifice. P. 314. 



Fig. 364. A a front view of the flute organ pipe, of wood, which is tuned by a 

 plug. B a section of the pipe. P. 314. 



Fig. 365. A stopped diapason organ pipe, of metal. It is tuned by altering the 

 position of the pieces on each side of the mouth. P. 314. 



Fig. 366. A chimney pipe. P. 314. 



Fig. 367. A spindle shaped organ pipe, contracted above. P. 314. 



Fig. 368. A the form of a cromorn pipe, B, of a trumpet pipe, both having reed 

 mouth pieces. P. 315. 



Fig. 369. A ray or pencil of light A B, C B, falling on the surface D E, a por- 

 tion of the light is reflected, and another portion is transmitted, in the direction 

 B F, B G, so that B G is equal to B C, and B H to B I, C I K and G H L being 



