783 



PLATE XXVI. 



Fig. 357. The right half of the human larynx. 

 ABC is the outline of the cricoid cartilage, DEFGH 

 of the thyreoid, and I K L of the arytaenoid cartilage; 

 M is the epiglottis,NK the upper ligament ot the glot- 

 tis, OP the lower ligament, and Q, the trachea. P. 400. 



Fig. 358. A view of the ligaments of the glottis, 

 seen from above, the larynx being divided by a hori- 

 zontal section a little above them. P. 400. 



Fig. 359. Sections of the pipes employed by Kratz- 

 ensteln for producing the sounds of the different vow- 

 els ; in general by means of a larynx resembling the 

 moutli 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. 401. 



Fig. 306. Tiie vox humana organ pipe, with the 

 mouth piece common to reed pipes in general ; the 

 lower part in contact with the tongue being nearly sc- 

 micylindrical : the tongue being adjusted to the pro- 

 per pitch by means of a sliding wire, which regulates 

 tlie length of the part that is at liberty to vibrate. P. 

 40i. 



Fig. 361. The mouth piece proposed by Kratzen- 

 stein, 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. 401. 



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

 401. 



Fig. 363. A front view and section of the open 

 diapason organ pipe of metal. It is tuned by open- 

 ing or contracting the upper orifice. P. 402. 



Fig. 364. A a front vievr of the flute organ pipe, 

 of wood, which is tuned by a plug. B a section of 

 the pipe. P. 402. 



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. 402. 



Fig. 366. A chinmey pipe. P. 402. 



Fig. 367. A spindle shaped organ pipe, contracted 

 above. P. 402. 



Fig. 368. A the form of a cromorn pipe, B, of a 

 trumpet pipe, both having reed mouth pieces. P. 403. 



Fig. 369. A ray or pencil of light A B, C B,.falUnjr 

 on the surface D E, a portion of tiie light in reflected, 

 and another portion is transmitted, in the direction 

 B F, B G, so tliat B G is equal to B C, and B H to B I, 

 C I K and G H L being lines perpendicular to D E at 

 any such distances, that BK may be to B L in a cer- 

 tain proportion, which is that of the sines of the angles 

 of incidence ABM, C;B M, to those of the angles of re- 

 fraction F B N, G B N. B O and B P are tlie reflected 

 portions of the rays. P. 411. 



Fig. 370. A mode of determining the position of a 

 refracted ray, which is particularly convenient in the 

 case of refractions at spherical surfaces. ABC being 

 any circle, either touching the refractive surface at A, 

 or being itself a section of Uie refracting substance, if 

 another circle D E F be drawn on the same centre, 

 having its diameter to that of the first as the sine of 

 the angle of incidence to that of refraction, and a third 

 circle G H I, which is less than the first in the same 

 proportion as the second is greater; and if the direction 

 of the incident ray K A be continued to D, andLD be 

 drawn from the centre, cutting G H I in G, A G will be 

 the direction of the refracted ray: and if this ray 

 pass again out of tlie denser medium at B, its direc- 

 tion BM may be found by drawing LIF, and FBM 

 will be thus truly determined. P. 411. 



Fig. 371. A ray or pencil A B, refracted at B to C, 

 and there reflected by a perpendicular surface into an 

 opposite direction C B, will return also in the direction 

 B A, a portion of it being reflected, in the first place to 

 D, and in the second to E. P. 412. 



Fig. 372. A pencil A B passing through a substance 

 CD contained between parallel surfaces, continues its 

 course in the direction E F parallel to A B. P. 413. 



Fig. 373, The ray AB, entering the medium CD 

 through the transparent substance E F, contained be- 

 tween parallel surfaces, acquires the direction Gil, pa- 

 rallel to IK, into which LI is at once refracted. P. 

 413. 



Fig. 374. The appearance of a prism, of which the 

 lower surface is divided into a bright and a dark por- 

 tion, separated by a coloured arch A B C. P. 414. 



