OPTICS. 
recently invented by Dr. Brewfter, who obtained a patent 
for it; and gave it the above name, from its property of 
‘‘ creating and exhibiting an infinite variety of beautiful 
forms. 
The inftrument in its fimpleft form confifts of two 
refle«iling planes, inclined to each other, made either 
of two plates of glafs, blackened or filvered, or two me¬ 
tallic furfaces, or the two inner furfaces of a folid prifm 
of glafs, or rock-cryftal, from which the light buffers total 
reflection. The plates may be of any length ; but that 
•which is moft convenient will be found to be from five to 
ten or twelve inches ; or they may be made only two, 
three, or four, inches long, provided diflincl vifion is ob¬ 
tained at one end, by placing at the other end an eye- 
glafs whofe focal length is equal to the length of the re- 
fleCting-plane; their breadth fhould be about eight or 
nine tenths of an inch when the length is fix inches; but 
it fhould increafe with the length, in order to have the 
aperture of the fame angular magnitude. Two edges of 
thefe reileftors, being made perfeftly ftraight, are placed 
together by a particular contrivance, in f'uch a manner, 
that their'inclination, or the angle which they form, is 
exaClly an even aliquot part of a circle, or a fourth, fixth, 
eighth, tenth, twelfth, fourteenth, &c. part of 360°. When 
the plates are thus fixed in a tube, and the eye placed at 
one end, as near as can be, in the line of the interfeSion 
of the two planes, it will perceive a circular field of view, 
compofed of as many luminary fettors as the number of 
times the angle formed by the refieClors is contained in 
360°. Thefe feCloj’s, excepting the one feen by direCt 
vifion, and conftituting the angular aperture of the plates, 
are a feries of images of this aperture, formed by fuccef- 
five reflections between the inclined reflectors. The 
images formed by one reflection from each of the plates lie 
oat each fide of the direCt aperture, and are inverted images 
of that aperture ; the next two images formed by two re¬ 
flections, are images not inverted ; and fo on throughout 
the whole feries, every two direCt images being feparated 
by an inverted one. 
The tube which holds, the reflecting plates moves in 
another tube; and upon the outer end of the laft tube"is 
placed a cell, or cap, for receiving^ feries of objeCt-plates, 
containing fragments of differently-coloured glafs, and 
other fubftances, placed at random. When one of thefe 
objeCt-plates is placed in the cell, the inner tube is puflied 
in as far as it will go; and, the inftrument being held in 
one hand, the cell containing the objeCt-plates may be 
moved round with the other, or the whole inftrument may 
be moved together ; and the eye, being placed at the 
other end, will obferve the irregular mafi’es of objeCts ar¬ 
ranged in an infinite variety of forms, mathematically 
fymmetrical, and highly pleating to the eye. When the 
tube is put in motion, the combination of images will 
likewife be put in motion ; and new forms, perfectly dif¬ 
ferent, but equally fymmetrical, will fuccefiiveiy prefent 
themfelves; fometimes varying in the centre, fometimes 
emerging from it, and fometimes playing around it in 
double and oppofite ofcillations. When the objeCts are 
tinged with different colours, the moft beautiful tints are 
developed in fuccefiion ; and the whole figure delights the 
eye by the perception of its form, and the brilliancy of its 
colouring. 
In this fimple form the kaleidofcope became a common 
toy abouttheyear1816 or 17. In July 1817, Dr.Brewfter 
took out a patent; and in the year 1S19 he publiflied 
a pamphlet containing a defcription of it in the different 
forms it is fufceptible of. This fmall work is ornamented 
■with feven plates, from which we fliall felect as many 
figures as will fill one of our own, and will make the 
principle of the invention perfectly clear to the reader. 
Alluding to the beautiful forms which are produced by 
this inftrument from broken bits of glafs, beads, minute 
dippings of lace, &c. the doCtor has prefixed to his de¬ 
fcription of it, the appropriate motto of J\’ikil taugit quod 
nonomat; which motto, when we advert to his curious 
cm 
experiments and difeoveries, particularly in optics, might 
be juftly applied to the doftor himfeif. 
The fteps by which Dr. B. was led to the invention of 
this inftrument, we fliall give in his own words. “ The fir ft 
idea of this inftrument prefented itfelf to me in the year 
1814, in the courfe of a feries of experiments on the po- 
larifation of light byfuccefllve reflections between plates 
of glafs, which were publiflied in the Philofophical Tranf- 
aClions for 1815, and which the Royal Society did me the 
honour to diftinguifli by the adjudication of the Copley 
medal. (See p. 559. of this article.) In thefe experiments, 
the reflecting plates were neceffarily inclined to each other, 
during the operation of placing their furfaces in parallel 
planes; and I. was therefore led to remark the circular 
arrangement of the images of a candle round a centre, 
and the multiplication of the feCfors formed by the ex¬ 
tremities of the plates of glafs. In coi'.fequence, how¬ 
ever, of the diftance of the candles, &c-. from the ends 
of the reflectors, their arrangement was fo deftitute of 
fymmetry, that I was not induced to give any farther at¬ 
tention to the fubjeft. On the 7th of February, 1815, 
when I difeovered the development of the complemen¬ 
tary colours by the fucceflive reflections of polarifed light 
between two plates of gold and filver, the effects of the 
kaleidofcope, though rudely exhibited, were again forced 
upon my notice; the multiplied images were, however, 
coloured with the moft fplendid tints ; and the whole ef- 
feCt, though inconceivably inferior to the creations of the 
kaleidofcope, was ltill far fuperior to any thing that I had 
previously witneffed. In giving an account of thefe ex¬ 
periments to M. Biot, on the ( 5 th of March, 1815, I re¬ 
marked to him, that, when the angle of incidence (on the 
plates of filver) was about 85° or 86°, and the plates al- 
moft in contaCt, and inclined at a very fmall angle, the 
two feries of reflected images appeared at once in the form 
of two curves ; and that the fuccefiion of fplendid co¬ 
lours formed a phenomenon which I had no doubt would 
be confidered, by every perfon who faw it to advantage, 
as one of the moft beautif ul in optics. Thefe experiments 
were afterwards repeated with more-perfeCtly polifhed 
plates of different metals, and the effects were propor- 
tionably more brilliant; but, notwithftanding the beauty 
prifing from the multiplication of the images, and the ad¬ 
ditional fplendour which was communicated to the picture 
by the riclvnefs of the polarifed- tints, it was wholly defti- 
tute of fymmetry; as I was then ignorant of thole posi¬ 
tions for the eye and the objects, which are abfolutely ne- 
ceffary to produce that magical union of parts, and that 
mathematical fymmetry throughout the whole picture, 
which, independently of all colouring, give to the visions 
of the kaleidofcope that peculiar charm, which diftin- 
guifhes them from all artificial creations. 
“ Although I had thus combined tvvp plain mirrors, fo 
as to produce highly pleafing effeCts, from the multiplica¬ 
tion and circular arrangement of the images of objeCts 
placed at a diftance from their extremities, yet I had- 
fcarcely made a ftep towards the invention of the kaleido¬ 
fcope. The effeCts, however, which I had obferved, were 
fufficient to prepare me for taking advantage of any fug- 
geflion which experiment might afterwards throw in the 
way. 
“ In repeating, at a fubfequent period, the very beau¬ 
tiful experiments of M. Biot, on the aCtion of homoge¬ 
neous fluids upon polarifed-light; and in extending them 
to other fluids which he had not tried, I found it molt con¬ 
venient to place them in a triangular trough, formed by 
two plates of glafs cemented’together by two of their 
fides, fo as to form an acute angle. The ends being 
doled up with pieces of plate-glafs cemented to the other 
plates, the trough was fixed horizontally for the recep¬ 
tion of the fluids. The eye being neceffarily placed with¬ 
out the trough, and at one end, forne of the cement, 
which had been preffed through between the plates at the 
objeCt end of the trough, appeared to be arranged in a 
manner far more regular and fymmetrical than I had be¬ 
st fore 
