414 



KALEIDOSCOPE. 



[ 



F'ig <>, where AP, is the tube, A its object end, and B 

 its eye end, am! (' H cell. which holds the circular object 

 plated 1). and has a groove for admitting rectangular 

 object plat,-. This cell is placed on the end A of the 

 tube, and turned round by the hand while the eye is 

 applied at B. Wiu:n the rectangular object plate is 

 u-ed, it is placed in the groove of the cell C, and moved 

 hat-kw.srds and forwards in this groove, while the cell 

 itself may be either stationary, or moved round its axis. 

 Hv this means the most splendid patterns are produced, 

 and the singular effects arising from the different direc- 

 tions, in which the objects cross or enter the angular 

 aperture, are displayed in a striking manner. 



The patterns may likewise be varied, by placing the 

 different sides of the object plates next to the instru- 

 ment, though in general the clear glass should be near- 

 est the eye. Other changes of form may be produced 

 by a pencil or ink. or by varnish or fransparent paint 

 laid at random on the ground side bf the plate. 



One of the object plates is made less in diameter than 

 the rest, in order that it may lie loose in the cell D, and 

 vibrate by the slightest motion of the hand. The effect 

 of this vibration is singularly fine, particularly when it 

 is combined with the motion of the coloured fragments 

 in the object plate. The best method of producing the 

 vibration, is to strike slightly with the finger on the end 

 N of the tube. 



Another of the object plates, in several of the instru- 

 ments, contains either fragments of colourless glass, or 

 an irregular surface of transparent varnish or indurated 

 Canada balsam. This object plate gives very fine co- 

 lourless figures when used alone ; but its principal use 

 is to be placed in the cell between an object plate with 

 bright colours and the end of the instrument. When 

 this is done, the outline of the pieces of coloured glass 

 are softened down by the refraction of the transparent 

 fragments, and the pattern displays the finest effects of 

 soft and brilliant colouring. The colourless object 

 plate supplies the outline of the pattern, and the mass 

 of colour behind fills it up with the softest tints. 



When the instrument is used in candlelight, the end 

 of it, N, should be held within an inch or two of the 

 candle, and a little to one side of it, or should be di- 

 rected to a point half way between two candles placed 

 as near each other as possible. The light of an Argand 

 lamp is, however, preferable to that of a candle. 



If the observer wishes to look at any other object not 

 contained in the object plates, he has only to remove 

 the cell D, and hold the object dose to the end N of 

 the instrument ; for the symmetry of the figure is des- 

 troyed if it is kept at a distance, or if the tube MO is 

 pulled out in the slightest degree. Hence it will be 

 found that the pattern is most perfect when the object 

 is actually placed upon the fixed glass at the end N of 

 the tube OM. 



In looking at opaque objects, as a seal, a watch-chain, 

 the seconds hand of a watch, coins, pictures, gems, 

 shells, flowers, leaves, and petals of plants, impressions 

 from seals, c. the object, instead of being held between 

 the eye and the light, must be viewed in the same man- 

 ner as we view objects through a microscope, being al- 

 ways placed as near the instrument as possible, and so 

 as to allow the light to fall freely upon the object. The 

 object plates A, B, C, &c. and all transparent objects, 

 may be viewed in this manner: but the most splendid 

 exhibition of this kind is to view minute fragments of 

 coleuced glass, &c. placed in a flat box, the bottom of 

 which is made of mirror glass. An object plate of this 

 description accompanies some of the instruments. 



SECT. VI. On the Compounilor Telescopic Kalddo. J^"^ 



XCIIllC. ^ ' 



IN using the simple instrument, which we have just 

 described, the observer is often disappointed at not be- 

 ing able to produce a perfectly symmetrical pattern 

 from opaque objects, from objects which are necessarily 

 at a distance from the instrument, or from those which 

 have such a magnitude that they cannot be introduced at 

 the aperture AOB. The power of the instrument, in- 

 deed, in its simple form, is limited to transparent objects, 

 or to the outlines of opaque objects held close to the aper- 

 ture. A method of removing this limitation, wnl of ex- 

 tending indefinitely the use and the application of thein- 

 strument, soon suggested itself. It occurred to Dr. Brew- 

 ster,thatifMN,Fig.7,wereadistantobject,eithei opaque PI.ATE 

 or transparent, it might be introduced into the picture by CCCXLI. 

 placing a lens LL at such a distance before the aperture t>s ' 7- 

 AOB, that its image might be distinctly formed upon 

 the plane passing through AOB. By submitting this 

 idea to experiment, he found it to answer his most san- 

 guine expectations. The image formed by the lens at 

 AOB became a new object, as it were, anil was multi- 

 plied and arranged by successive reflections in the very 

 same manner as if the object MN 7 had been reduced in 

 the ratio of ML to LA, and placed close to the aper- 

 ture. 



The compound kaleidoscope is therefore fitted up as 

 shewn in Fig. 1. with two tubes AB, CD. The inner 

 tube AB contains the reflectors as in Fig. 6. and at the 

 extremity C of the outer tube CA is placed a lens which 

 may be taken off or put on at pleasure. The focal 

 length of this lens should always be much less than the 

 length of the outer tube CA, and should in general be 

 such that it is capable of forming an image at the end 

 of the reflectors, when A B is pulled out as much as pos- 

 sible, and when the object is within three or four inches 

 of the lens. When it is required to introduce into the 

 picture very large objects placed near the lens, another 

 lens of a less focal length should be used, and when 

 the objects are distant, and not very large, a lens 

 whose principal focal length is nearly equal to the great- 

 est distance of the lens from the reflectors should be 

 used. 



When this compound kaleidoscope is used as a simple 

 instrument for viewing objects held cloje to the aper- 

 ture, the tube AB i.s pushed in as far as it will go, the 

 cell with the object plate is slipped upon the end C of 

 the outer tube, and the instrument is used in the same 

 way as the simple kaleidoscope. 



In applying the compound kaleidoscope to distant 

 objects, the cell is removed, and the lens LL substituted 

 in its place. The instrument is then directed to the 

 objects, and the tube AB drawn out till the pattern 

 appears perfectly symmetrical. 



When the object is about four inches from the leris, 

 the tube requires to be pulled out as far as possible, 

 and for greater distances it must be pushed in. The 

 points suited to different distances can easily be deter- 

 mined by experiment, and marked on the inner tube, if 

 it should be found convenient. In most of the instru- 

 ments there is, near the middle of the tube O M, a 

 mark which is nearly suited to all distances beyond 

 l/.reejfcei. The object plates A, B, C, &c. held in the 

 hand at a distance greater than five or six inches, may 

 be also used when the lens L is in the tube. The fur- 

 niture of a room, books and papers lying on a table, 

 pictures on the wall, a blazing fire, the moving foliage 



