The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1879-03-14
,Torn;uG Mirage.
r.,l!layT EXHIBITION OF THE PHENOMENA
N DAKOTA.

N DAKOTA.
From The -. raui Pionecr-PresE.l
", have had some still. clear. and very
~! ni.lI, this winter. followed by bril-
... i4wns. which have been peculiarly
..g..'ic 10 the display OF the remarkable
,.sg9mcna commonly known here as
".rrnir. mirage" Dwcllcrs on the prai-
r., uA1 are M betime>. looking to any
..n: o.: the COM lass but the north, sec on
,r4 mornings. shortly before sunrise, 4
,.-a more distant horizon than usual.
J. .. @aG miles 81 country. ordinarily cut
q. ION The view by rising ground or belts
Q. ,.sr-r will he raised. aS it were. above
-ra','ar)c>. Town, and other prominent
'@e., twenty iuilae away are no longer ~
l,D.c. but are clearly revealed, with II!
1T liz, between them and the spectator.
TIE windows nav be counted in houses
=. at other times can no more be seen
,:sa / they We're at the antipodcs. and near
ir.t>, usually Just within the range OF
I'.sN, SEEN 70 nc brought much closer. AS
- >p3 orb li>es above the AOlHon the
''lJA sink, below II. While it lasted Il
Nm might ">ee through brick WALL
,..ch in The hlI-i!lv,t noon will form IN
"-,.@etrabic barrier 10 his view. An cX-
.' a1l aware. 10 be found in Our text
'r'G.@A pay.;r>. The one generally given OF
l." mirage o. the desert explains very little
g. what /, seen there and Is wholly lnappli-
@'ir % TIE morning mirage Of northern
-'lic>. The following explanation, which
j. .2>ed upon laws observed in connection
"@'ae wave theory Of light. may, there
!..s' ne new ard interesting TO some OF
!Jl- readers:
Morning mirage" is what IS called
terrestrial rcir%ction cXtraoI dinarily m
led By a coincidence Of conditions only
W I've met with where the atmosphere IS
's'! 900. dry, and clear, and the latitude
d, - lar south ihat the sun rises rapidly,
zen ID winter. =: the end OF a still! night,
"s'" IL" Thermometer some degrees below
30, 'ht almo> Ihcrc is not only At its great
-. density, hW i: probably retards The pas
-" iShi IN other ways unknown 10 us
=. l.r>eht. Optical effects observed in the
,'>'' regions favor the theory that this
''r>"'t rclardatioD j. due 10 iowncSs Of
'',,"IFe or some accompanying coMdl-
' ~ me atmosphere not indicated by
49, 's''l0r(cr. But the rising sun raises
I.a ""'a'urr and lessons the density OF
,.,' ie-!on> Of the air within our range
., ~, ,",h before il affects the lower, just rs
,...,,'"e moua.oiu tops before its beams
.r ,II , '1e pain. The difference Of density
.~>;, %"'Irfalnse increases very rapidly, |
evan ,' ~ ne considerable power OF the sun,
TIA. "lSA'h month OF the winter Solstice.
fr..,;l" '.Iore Of the rays on territorial re-
ysg ..ron Is oWlns 10 the fact thar light
,: a.. .'' travels by the path which occ,l-
iw.rd I' IL, lc''! tine, and therefore deyiates
md 49, ."e f;r"r part of the atmosphere,
g,1alI'. 'a0Fh'hy mirage results from an I'M
If >~:.;, s'eep deviation. The appearance
3, We. ''e Is always accelerated at this time
4. 49, more than that Of sunset is retard-
= , nut on The mornings when, owing to
lq r'a'y. caitnnes3 Of the atmosphere, the
nvS s e., o. temperature takes place in hori-
tly mahes, Terrestrial objects considera- !
ato,e inc horizon Will seem to be raised |
e4e.1r ~A''l the lower strata OF air, being
4ssef % ssd wilh the upper, there is no
caiya,nru !tain@ 10 cause the excessive |
s:hf. VI the course OF the waves OF |