938 CAT 
that is intended to be reprefented on the outfide of the 
partition, in an inverted poiition, which fuppofe a flower, 
figure, picture, &c. Before the partition, and below the 
aperture, place a flower-pot, D, or other Suitable pededal, 
fo as the flop may be even with the bottom of t he aperture, 
and that the eye, placed at G, may fee the flower in the 
fame poiition as if its (talk came out of tIre pot. The fpace 
between the back part of the partition and the mirror mull; 
be painted black, to prevent any extraneous light being 
reflected on the mirror; in faff, the whole (hould be fo 
dilpoled, as to be as little enlightened as pollible, for the 
proper management of the light and fhade is as material as 
any other part to the experiment: tire ftrength and bold 
effeCt of the image depend entirely upon it; and, for want 
of this precaution, many attempts have failed, and the ex¬ 
periment ignorantly depreciated. When a perfon is placed 
at G, he will perceive the flower or other objeCt placed 
behind the partition ; but, on putting forward his hand to 
pluck it, he will find that he only grafps at a phantom. 
Fig. 17 reprefents a different poiition of the mirror and 
partition, and better conftruCted for exhibiting effeCt by 
various objedts at the inftant. A is a thin partition of a 
room from the ceiling down to about two feet and a half 
from the ground. B, a continuation of it, with an aper¬ 
ture for a good convex lens turned outwards into the room 
nearly in an horizontal diredtion, proper for viewing by 
the eye of a perfon (landing upright from the floor or foot- 
ftool. C, a continuation of the partition to the ground, 
fo as to exclude every obfervation of the internal arrange¬ 
ment from the fpeCtator on the outfide. D is a large con¬ 
cave mirror, fupported at a proper angle, to relledt up¬ 
wards, through the glafs in the partition B, images of ob¬ 
jedts at E, prefcnted towards the mirror below. A ftrong 
light from lamps, Ac. is to be diredted upon the objeCt, 
and no where elfe ; and to the eye at F, it is truly furpri- 
fingand admirable to what effeCt the images are refledted 
up into the air at G. It is from this arrangement that 
fhowmen excite the ignorant to the furprize of wonderful 
apparitions of various kinds of objeCts, fucli as a relative’s 
features for his own, paintings, of portraits, plalter figures, 
flowers, fruit, fvvord, dagger, death’s head, &c. all calcu¬ 
lated to produce a fudden effeCt upon the mind or imagi¬ 
nation. 
To caitfe the appearance of a flower from its aflies .—A con¬ 
cave mirror is here agam the material article in the ma¬ 
chine. Fig. 18. A8CDEF reprefents a wooden box, 
about tw o feet and a half high at AC, fifteen inches at DF, 
and, for length, eighteen to twenty inches; and its breadth, 
DH, about twelve inches. In an opening made in the 
fide B K, place a glafs bottle, fix inches in diameter, which, 
fitting exadfly the aperture, difguifes the mirror N. A pa- 
paper circle, O, of fix inches diameter, containing a bar 
magnet fufpended by a fine thread for a centre, underneath 
the part EG. Four fmall neat artificial flowers are to be 
fixed to the circumference of the card, at equal diftances, 
and fo adjufted as by the mirror to be refledfed in the bot¬ 
tle M. The infide of the box is to be made black, and, 
by a door at P, a light intioduced at Quoting all the ne- 
ceffary precautions for light and darknefs, as directed in 
the preceding- experiments. A final! fquare box mull alfo 
be provided, about fix inches fquare, having, four com¬ 
partments, and a correfponding magnetical bar concealed 
infide. In either of thefe four (quares, the allies of the 
burnt flower, fimibr to one of the four on the circle, is to 
be depofited, and the box placed at top, S, by a private 
mark made for tl at purpofe, and in fuch a poiition that the 
attraction of the magnet may bring the proper flower be¬ 
fore the mirror N. A perfon, with his eye at fome dilhtnce 
from the bottle M, will then perceive, to his furprize, the 
flower in it that he law had been burnt to athes. Any of 
the fouraflhes might be previonlly named, and the appear¬ 
ance of the flower reffored in an inftant. 
The Catoptrical Perspective Box. 
Fig. i‘j reprefents a box, containing a concave mirror 
CAT 
at its end AC ; the length may be from eighteen inches to 
tw-o feet ; the breadth and depth according to the diame¬ 
ter of the mirror tiled. At I L is introduced a blackened 
partition to hide the frame of the mirror, and the hole cut 
in it is large enough to admit the view of the objeCt to be 
placed at BEFD. The top of the box (hould be covered 
clofe from A to I ; the other part, IB, may be covered 
with glafs lined with gauze or paper. An aperture for 
both eyes rruift be made above, at G, and under this may 
be placed drawings, paintings, &c. which either by night 
or day rnuft be illuminated as ftrongly as pcflible. By 
this (imple conffruCtion, a very beautiful and perfpeftive 
view of the objeft will be had, and in a manner very pleaf- 
ing and entertaining. If a perfpective view' of a landfcape, 
fliipping, &c. be painted on three pieces of glafs, and placed 
about an inch apart at the inner end of the box BF, and 
fo much of the end of the box cut out as to admit the 
rays of the fun, or the light from wax candles placed in 
a tin box behind them, it will afford one of the moft en¬ 
chanting view s that can be imagined ; the picture will ap¬ 
pear actually extended like nature, and all the various 
fubjeCts under a relief much more perfeCt and bold than 
to the common eye without the mirror. In this apparatus, 
the more the mirror is darkened, and the more the objects 
are illuminated, the ftronger will the effeCt be. Common 
perfpective prints of buildings, &c. itfually fold with the 
common diagonal print machines, wdien perforated at dif¬ 
ferent parts, fuch as the windows, &c. and tranfparent 
coloured paper applied thereon, have alfo a very pleafing 
efieCf in the box, and give the appearance of illuminations 
by night. 
The Cylindrical Mirror. 
A concave cylindrical mirror, which is a glafs ground 
by the revolution of a cylindrical tool turning 011 its axis, 
produces two or three curious and entertaining elfeCts. 
The face prefented to one mounted in a fquare frame will 
appear in one direction elongated, or, in a vertical direc¬ 
tion, deformed in an extraordinary manner. Jf the mir¬ 
ror be turned a quarter round, the face will be extended 
in a limilar way but horizontally. A finger placed to 
the right fide of the nofe, while the race is. within the 
focus of the mirror, will appear as in a plain mirror; bur, 
if the face and finger together be carried backwards in 
the axis of the glafs beyond the focus, the finger will in a 
lingular manner appear on the reverie fide, though every 
other part of the face appears unaltered. The cattle is 
from the mirror having only a longitudinal focus, in one 
direction, and that in the cylindrical direction of its curve. 
Fora deferiptien of other fimilar articles of catoptrical 
illulion, fee Recreations by hooper, and in French by 
Gnvot. 
CATOP'TRIC ClS'TULA.yi A machine, or appara¬ 
tus, by which fmall bodies are reprefented extremely 
large, and near ones extremely wide, and dtifufed through 
a vaft fpace ; with other very pleafing phenomena, by 
means of mirrors, difpofed by the law s of catoptrics, in 
the concavity of a kind of clieft. See feveral of.thefe ex¬ 
plained in the preceding article, and reprefented in the 
engraving. 
CATOP'TRIC-DI'AL,/. A dial that exhibits objeCts 
by reflected ravs. See Dial. 
CATOP'TRIC TE'LE,SCOPE, [ A telefcope that 
exhibits .objects bv reflection. See Telescope. 
C A I O P’TR OMAN C V-j f. [from Kce.T07P.fov, fpeculum , 
mirror, and fj.a.vTe i«, divinatio, 'divination. ] A kind of di¬ 
vination among the ancients; fo called, becaufe confiding 
in the application of a mirror. Paufanias fays, it was in 
ufe among the Achaians ; where thofe who were lick, and: 
in danger of death, let down a mirror, or looking-glafs, 
fattened by a thread, into a fountain before the temple of 
Ceres; then, looking in the glafs, if they fawa ghaftly 
disfigured face, they took it as a fure frgh of death: on 
the contrary, if the fiefh appeared frCfti and healthy, it 
was a token of recovery. 
C ATORE'TICS, 
