45 



KALEIDOSCOPE. 



40 



K 



has the same sound which C has before the vowels a, o, v. A 

 reference to that consonant will therefore suffice for the power 

 of the letter ; its various forms may be seen in ALPHABET. Although 

 this letter is now superfluous, it was not so when the characters of 

 an alphabet were syllabic in power. Thus the letter I- appears to 

 have denoted at one time the syllable lea, while another character 

 represented ko, and so on. Hence'in the Greek and Hebrew alphabets 

 the former was called /'//./'". ///</<: the latter kr/fipa, koph. This 

 accounts for the fact, that in Latin the letter t was never used except 

 before the vowel a, precisely as q is found only before w, and the 

 Greek koppa only before o. Even our own alphabet seems to imply 

 such a limit in the use of this consonant, when it gives it the name 

 ka,notke; though the latter name would better agree with le, ce, 

 de,kc. 



KAKODYL. Synonymous with CACODYL. 



KAKOPLATYL. [CACOPLATYL.] 



KAEMPFERIDE. A yellow inodorous crystalline substance con- 

 tained in the root of the Gatanga (Kaempfcria Galanga). It fuses 

 below 212 Fahr. and dissolves in 25 parts of ether at 60. It 

 consists of 



Carbon 



Hydrogen 



Oxygen 



. 05-3 

 . 4-3 

 . 30-4 



100-0 



KALEIDOPHONE. [ACOUSTICS.] 



KALEIDOSCOPE, a name compounded of two Greek words (*oAis 

 and ovcoiros), and denoting the exhibition of beautiful forms, is the 

 designation of an optical instrument which was invented by Dr. (now 

 Sir David) Brewster, and patented by him in 1817. 



About three years before that time Sir David Brewster, being 

 engaged in making experiments on the polarisation of light by reflec- 

 tion, from plates of glass, observed that when two plates were inclined 

 to one another, and the eye of the spectator was nearly in the pro- 

 duced line of the common section of their planes, the farther ex- 

 tremities of the plates were multiplied by successive reflections so as 

 to exhibit the appearance of a circle divided into sectors, also 

 that the several images of a candle near those extremities were 

 circularly disposed about the centre ; and these circumstances sug- 

 gested to him the construction of an instrument of the kind above 

 named. 



It may be observed, however, that the multiplication of the image 

 of an object by successive reflections from mirrors inclined to one 

 another had long before been a subject of investigation in treatises on 

 optics ; and both Baptista Porta and Kiruher had given descriptions of 

 instruments consisting of mirrors united at two of their edges, which, 

 being opened like two leaves of a book, were capable of multiplying 

 the images of objects. Bradley also, about the year 1717, constructed 

 an instrument consisting of two plates of glass inclined to one another, 

 which being placed on a drawing, with the line of section perpendicular 

 to the paper, exhibited to the eye several images of the figures, dis- 

 posed by successive reflections about a centre. But the optical inves- 

 tigations alluded to are very remotely connected wUh the properties of 

 the kaleidoscope ; and the application of the latter to objects which 

 may be moveable and situated at any distances from the observer, 

 render Brewster's instrument very different from and far superior to 

 the simple contrivances of Porta, Kircher, and Bradley. 



The essential parts of the instrument consist of two plane mirrors 

 of glass, having their posterior surfaces blackened in order to prevent 

 any reflection of light from thence ; mirrors of polished metal would, 

 however, be preferable : each mirror is from six to ten inches long, 

 ami of a trapezoidal form ; the larger end about an inch and a-half 

 long, and the shorter end about three-quarters of an inch ; and the 

 two are placed in contact with one another at a long end of each, so 

 as to form a dihedral angle, the like ends being placed together : the 

 objocl to be viewed i-i disposed contiguously to the larger ends, and 

 the eye should be near the opposite extremity, but a little above the 

 -[contact. The effects produced by the reflections of the light 

 may be understood from the following considerations : 



Let A c, B c, in the first of the figures, be the two extremities of the 

 mirrors on the side farthest from the eye of the observer, which is 

 supposed to be near the opposite extremity of the line of section 

 passing through c perpendicularly to the plane of the paper. These 

 lines A c, B c, and the sectoral space between them (which in the figure 

 is one eighth part of a circle), will be visible by rays coming directly 

 to the eye ; and, at the same time, rays from the line A c falling on 

 the mirror B c at a certain angle of incidence will, on being reflected 

 from thence to the eye, give rise to the image ca of that line; in Hk 

 manner rays from the line B c falling on the mirror A at an equal 



angle of incidence will, after reflection, give rise to the image c 6 of 

 the line. These, with the intermediate rays, produce the first reflected 

 sectors B c o and A c b. Other rays from- the sector A c 6 at the surface 



of the mirror A c will fall on the mirror B c ; and, while a portion of 

 them arrive at such angles of incidence as to be reflected to the eye 

 and produce the perception of the sector a c b', another portion of 

 them will be reflected back to the mirror A c at such angles of incidence 

 as to be re-reflected to the eye and cause the perception of the sector 

 a'c If'. In a similar manner the rays first reflected from BOO will, by 

 subsequent reflections, give rise to the perceptions of the sectors 6 c a', 

 I' c a". 



Thus it is easy to perceive that an object, as M, on A c, with its 

 immediately reflected image M', will give rise to the appearances of 

 similar figures at mm 1 , m"m'"; and an object, as N, on A B, with 

 its immediately reflected image N', will give rise to the appearances 

 of similar figures at n n', n" n'" : also an object, as P, between A c 

 and B c, will appear by reflection similarly situated in all the other 

 sectors. 



vlf the angle A B be ^th of four right angles, in which m is any 

 term in^the series of even numbers 4, 6, 8, 10, 4c., the number of 

 sectors will be m, and each of them will be equal to A c B, while c Y, 

 the appearance of the line in which the mirrors meet each other, will, 

 as in the figure, bisect the angle which is opposite to A c B ; also if m be 

 any term in the series of odd numbers 5, 7, 9, &c., the number of 

 sectors will be m, and each of them will be equal to A c B, while c Y 

 will coincide with the line in which the two lowest sectors join one 

 another. It may hence be easily understood that if a flat object placed 

 in the sector ACS, with its plane perpendicular to the mirrors, have 

 its bounding-lines similarly situated with respect to A c and B c, the 

 reflected images will be similar and equal to the original object ; and 

 the whole will constitute one symmetrical pattern, whether the value 

 of m be odd or even : but if the bounding-lines are not similarly 

 situated with respect to A c and B c, the reflected images will not, in 

 the two lowest sectors, unite so as to correspond to the images in the 

 other sectors, unless m be an even number. The second figure repre- 

 sents a pattern produced by the objects represented in the sector 

 corresponding to A c B in the first figure. 



In order that the whole pattern in the field of view might possess 

 perfect symmetry about the centre c, it would be necessary that the 

 eye should be exactly in the direction of the line in which the glass 

 plates meet one another ; but in such a situation the reflected images 

 would not be visible : if the eye were far above the line of meeting, 

 the visible field of view would be sensibly elliptical, and the brightness 

 of the field would be diminished ; it follows, therefore, that the eye 

 should be near the smaller ends of the mirrors, and very little above 

 the line of their junction. Again, it may be readily understood that, 

 in order to permit the reflected images of objects to be symmetrically 

 disposed about the centre of the field of view, the object should be 

 exactly in a plane contiguous to the mirrors at the extremities which 

 are farthest from the eye ; for the line in which the planes of glass 

 meet each other appearing to pass through the common centre of the 

 visible sectors, if the object were placed on that line of junction, and 

 either between the eye and those extremities or beyond the latter, it is 

 evident, the eye being above the line of meeting, that the apparent or 

 projected place of the object would not coincide with that common 

 centre, but in the former case would appear below, and in the latter 

 above, that centre. The length of the mirrors should be such that the 

 object in the sector ACS may be distinctly visible ; the eye may, how- 

 ever, if necessary, be assisted by a concave or a convex lens. 



The first kaleidoscopes constructed by Sir David Brewster consisted 

 simply of the two mirrors, which were fixed in a cylindrical tube ; the 

 objects were pieces of variously coloured glass attached to the farther 

 ends of the mirrors and projecting on the sectoral space A c B between 



