St. Mary's beacon. [volume] (Leonard Town, Md.) 1845-1863, 1858-09-09
SELECTED MISCELLANY.
An Optical Pheaomenon.

The exc i, the mcSt wonderful "r.,an in tiic
human frame Ii j. the mcijum hy which
the tclcgraplir aZ"iI,I,., ii light carry orr per
v"p,ioIis in an instant III y,;rhl uI,~'rt. dis
tant millions "t miles, n IN the cas-" "i the
heavenly hnlcs Ia rcuu"ctipn with optics
also. the most cN'ra'rdiI any phenomena and
illusions occur We are all familiar. hy de-
Scriptinn AT least. with the Inirag" oI I'll" de
x,rt where the !tr cx xtcndmg plain assumes At
\ distance the appearance h = t.n". winch,
~ the thirsty traveller presses "a L. partIE"
..f its refreshing watrIs. rcCcdcS and disappears
before him. Accounts Of ships ~ -,
sailing in the Skv of douhlc SHIPS, anl ii
',nlics "i troops pictured on til" vicwlcrs air.
are also nunlcrDlIS amd all prnlal,Iy are tainii
iar with the phenomena nf in0mjHg lv winch
All Opposite shore seems tn he elevated
out of the water, or to be brought n"a'cr and
mountains, ships, or other uhitctS, appear L"
bc raised or nagnticd in dimensions. Thcsr
appearances arc caua'd by peculiar states {"
the atmosphere. by wrh the normal direction
al the rays If hight is changed. Omc of ;hc
most singular Of these optical phCaumcna has
been noticed recently a$ occurring iii the IVES
tern suburbs Ot Petersburg, VA an" "irScr
Sahlc daily from the residence of Doctor Duva
of that place The old B!antlfprd church.
which is distant about three miles, can be plain
" seen from mis- Iru,i,,, d,ui"ys thG 'utir"
morning; but abou: three O'Clock il the after
nnoiI il beg SinS tp disappear, assuming nrNt the
appcar:lIIce ni Il shadow, AMI finally, vanishing
altogether when objects situated behind the
church which col;d act be seen before hcco!nc
distinctly visible. Among these are the body
and lower branches of large sycamore tree
growing in the church yard view Of which
is completely intercepted by the body of the
church. but which. when t!e phcn hncnon ur-
ours. can be plainly seen trrn the green sward
at lis root TO it's topaz 1T leaf. Ills di>ai'-
pcarancc of an intervening object, and the
disclosing Of others tc the eye which should
should he hiA.lcn behind it. is very singular.
aud presents one of the most interesting cases
nf optical illusion we have ever met with. In"
regular repetition Of the occurrence is also OK
traor,iinarv. and would afford excellent oppor-
tuntl,S for invest CATION ~ tn tho causes ;s.'l
manner vi it, production. 4 valley intrrvcncs
6ctwccn the residence Of DR. Duvat and the
church, through which \ small stream of wa
ter passes and the rlty reservoir also les be
ncath the line of vision. The effect produced
Ilpnn the atmosphere bv the action of the .;i;i
upon the water intervening. causes, no d"uht
the singular illusion; but it would he dcsira-
bic tn have u more accurate solution OF the
phenomenon.
olls; sometimes they reside in the organ of Vi
sion itself sometimes III the mind but more
generally bv some circumstances which dis
furb the direct course Oi the rays OF light
Thus if 4 man places himself directly before 4
large cOncavc mirror, but further from IL than
thc centre q! its conCavity, he will see an in
verted image of himself in the :iir between him
and the mirror of 4 less size than himself: and
II he hold oTt his hand towards the mirror, the
hand of the image will come ont towards his
hand and coincide with it. of equal bulk
when his hand is in the centre Of the Conca-
vitv. and he will imagine that he mag Shlke
hands with his image. If he reach his hand
further, the hani of the image will pass hy his
hand and come between it and his body; and
r he nuve his hand t. either side, the hand Of
the image will move towards the other 50 thl,
whatever way the object moves, the image will
not appear to move the same. but the contrary
way. Yet hystander will see nothing of the
Image, because none of the reflected rags which
form il mcc: his eyes. Phrnnmcna of this
description all depend upon the fact that we
only see by the rays OF light reflected from an
Ubjcc: which meets orr eyes. II these rays are
intercepted or disturbed. we will either not see
the object. as in the case of the church ut
BandfDrd, or sec it distorted Is when we look
intO crooked mirror There are some extra
ordinary optica! Illusions rroluccd also as 10
Coiors occasionally. and perhaps every one has
sometimes noticed objects rs appearing To them
of u color which they know they are not Many
interesting occular spcctru may be produced ut
will. For instance, take rcd wafer place it
On sheet Of white paper, and closing one eye.
look steadily for some time ut the centre OF the
wafer, then turn the eye To another part Of the
paper, and YOU will see green wafer By
repeating the experiment with different colur$
black wafer will produce white, orange
blue, violet hlueish green image. each variety
Of hue presenting an image of = different tha;
is, its accidental or Opposite color. The plle-
nomena of the tnh morydnq seen in I'll. straits
Of Mcssina have never yet been satisfactorily
accounted for. When the rising sun throws
his n s. at an angle "f ~ degrees on the sea
of Rirgi" and neither wind nor rain ruff1e
the s.nopth surface Of the water in the bav.
the spectltur on an eminence in the city N!lu
places his back 90 the sun, and his face TO the
Aa, observes - it were upon its surface NUM- !
berleSs pilatcsss l:cher AMI castles t:isti:ict:y