El Paso herald. (El Paso, Tex.) 1901-1931, 1919-05-29
MirageS And
Their Causes;
Explanations
Have You Seen Villages,
Lakes and Forests Out
On the Desert"

Of course. you have seen cities and
temples and beautiful groves Of trees
and cool, refreshing Iakes-or thought
you did-on the desert" around FL
Pasos OF course. you have looked
down one Of FL Paso's long. Bituuthic
paved streets and seen it glimmering
with water" only TO find it as dry
as the proverbial bone on reaching il.
You knew it was a mirage. but did
you ever stop 70 wonder how it came
about, what caused it,
A lot Of people have been wondering
and some Of them have been about
these things recently 20 Scientific
publications. Scientific American has
been having lot about the phenom-
ena- one contributor says
Caused BY Reflection
1T has been my experience TO drive
for miles along the highway with al
the road, from a few hundred feet
ahead Of the car and behind IL to
the horizon in either direction, ap-
pearing like a lake-With trees,
houses and vehicles reflected lust as
a man has observed ia Ohio and Penn
sylTania- The 'wtaer' appears 70
evaporate ahead Of US and on looking
back IL seems 10 close in upon the
space through which we have passed.
The favorable condition for seeing
the mirage Is when the line OF sight
is close TO and parallel with the level
OF the road II the dag . only mod
erately dry and warm this line may
be about p inches above the road;
but sometimes, when heat and dryness
are excessive. as Is often the case
here. the mirage may be seen from a
height Of six OF seven feet
Ny theory is that the mirage is
caused rather by refraction than by
reflection from heated layer OF ar
INN eciately above the road After
the sun has been shining several
hours the air above the road Is heated
by conduction from the ground: and
when there is no wind or other ais
turbance the air at the ground is hot
test, and is cooler higher up-the
change in temperature being gradual
Is the height increases. The heated
air has a less optical as we'll as actual
density, 50 the light would follow
curved line
1T is to be noted that you cannot
see the feet OF the object, nor any
thing else on the ground about that
object because all the light leaving
the feet at an angle sufficiently
great not TO be totally reflected back
20 tha ground from the under sur
faces Of the layers Of air. viii be re-
fracted sufficiently 20 pass over the
obserVer's head.
The fact that this mirage can be
seen from different heights, depend
ing upon the temperature bears out
this theory. FOR. OF course the greater
the temperature the more difference
in the density Of the air Immediately
in contact with the road and that
some distance above IL. hence the
more bending Of the rays. and the
higher the position OF visibility for
given distance. The straight ray
Trrnrraf u-frf-n com IA L.
lively uniform. Is not interfered with
Al all BY the refracter pencil SO in
addition 20 the Inverted reflection
beneath the true object. tne observer
likewise sees the upper portions Of
tnat object IN its proper position
Common Street 1IlruEes.
Another man SAYS
The road mirage is very common
IN the streets Of some Of our cities
I first observed IL in Washington A
used a bicycle 70 get around with.
and as the mirage is visible mostly
from the middle Of the asphalt paved
street ana not from the sideWa K,
this may account for Its nouohserv-
ance by the majority. u consists ia
an appearance of Wetness, By the
blurred reflection Of passing objects.
on the pavement soE1e 500 70 1000 feet
away have never noted that IL cut
OF the lower part Of the object so
this must depend somewhat upon dis
tancs and other conditions It occurs
almost entirely on asphalt paved
streets occasionally on macadam
roads II is visible. moreover. no;
merely on warm, sunny days. but al
most equally on cold gray DAYS In
each case no doubt the sun is the
heating agent; but in the latter case
the heat is saved over from the last
sunny days, continuing TO make the
air layer Immediately above the pave
ment sufficiently warmer 10 produce
the total reflection 7 have seen the
mirage in Milwaukee. on asphalt and
in south Texas have observed il,
too or three times only, on an ordf-
nary prairie dirt road. Il is natural
that this mirage should occur more
frequently in southern climates than
in northern. hence it is probably more
cities
while on this subject I may point
out that the prairie mirage. whereby
trees, buildings and other objects or
the edge Of the horizon. three or
more miles away, are universally seen
in summertime separated by a layer
Of sky from the ground, IS just the
opposite Of the road mirage or OF the
desert mirage, 20 wit, the path OF
the visible ray is concave TO the
ground instead Of convex. This kind
Of mirage is the same as that seen
aH@A Ha~~aA al. " AANA ( a-ANAA- AAAa NAlAaA
u indicates that the air next the
ground is cooler than that Immediate
Il above"
Panhandle 1Iirages.
A Plainview, Tex, man says:
i have seen many miraEes ia the
Panhandle OF Texas, and our best
mirages are seen here between day
break and sunrise. although az this
altitude (3270 feet) the nights are
cool enough to require US 20 sleep
under bed clothing. Early spring is
the best mirage season here a
smooth OF hard surface is necessary.
as plowed ground does not give good
results. and on this account we are
seeing less mirages every year. Many
a morning ] have seen hills 80 miles
distant which are invisible ordinarily;
and occasionally get a peep at two
towns. and - minutes distant. re-
sDectively, which ordinarily cannot be
seen because OF their lying on lower
ground. have often wondered