The Washington times. [volume] (Washington [D.C.]) 1902-1939, 1918-01-08

II. r. LEIGH.
ETHER IS mistaken. I have
~ no copy OF my article at
IN hand, but it is my strong
Impression that in Il ] qualifed the
statement about rSinbows never
appearing as more than half-oir-
Giles by the words, except from 4
great elevation" or some eQuiva-
lent expression.
II did not use that qualification
IT was an oversight, which re-
Eret, and I will now endsavor to
atone for It by explaining why q
rainbow as ordinarily seen never
shows more than half q circumfer-
ence, and usually considerably less
than that, Although in certain cir
eamstancss it may show a full
circle
Remember. 10 begin with, that
the spectators back must be to the
sun, The drops OF rain in the air
being before him. while the sun.
whose rays they refrHGt, reject
and send back to his eyes, il be-
hind him Remember. also. that the
angle that the rays coming back
from the rAindrops make with 4
straight line drawn from the sun
through the observers head to the
centre Of the rainbow circle, is
about ~ degrees for the red, or
outside. rays Of the bow. and about
80 degrees for the violet or inside.
ray
Thus the bow, which is about two
degrees broad, cannot at Its outer
circumference be more than ~
degrees from the point where the
shadow OF the observers head Gf
It could Be sesn). would be pro
Jscted, which point ia. of course. the
centre Of the rainbow circle
when the sun Is on the horizon.
In q nat country. or at sea- the
shadow would fall on the opposite
horizon and the top Of the rain
bow arch would have an elevation
Of ~ degrees. and half Of Its circle
wsuid be. seen II the sun Is -
degrees high, the shadow will fall
- degrees below the plane OF the
horizon while the top OF the arch
will be lowered 20 degrees. and .
eorrsspondinSiJ smaller part Of the
full eircunfsrence Of the bow win
be visible
When the sun IL about 20 degrees
high. . little sector of the top Of
The arch may be visible night on
Ihs horizon. and IL the sun il a.
derreeG, or more, in elevation there
will be no rainbow seen at least
no primary bow.
Vow let Us consider the case OF an
observer who is elevated TO a great
height above the horizon a. on a
lofty mountain peak, or IN q bal
loon. In E1ch a situation IL 10 pos
Eibie 10 Sc the entire circle Of q
raInb bow. the lower half being no
longer concealed by the interposi-
ton of the earth
ThuA- standing on the edge Of the
Grand Canyon. with a precipice OF
thousands OF feet yawninK beneath
you, and With a rainbow formed
IN the rnists Of the canyon. between
you and its opposite wall, IL IL clear
hat IN fsvor4 BILE cirCu mstanceE. you
may Sc the entire circle OF the bow.
since your eye may range down
more than ~ degrees below the
center Of the bow without passing
from TIA uIFt-chargeo air 10 the
ground In other words. wherever
. line drawn from the sun through
your hsad would mark the center
~ > circle IN the 4ir So degrees in
dIzmeGsE- every part Of which would
he II 5ouT range OF vision, il would
he p0ssfbls for 4 complete circular
rainbow to appear 10 you
This interesting situation orcUrs
Besr many waterfalls. where Eteep
and high banks ovsrhanE a vast
chEBn into which the waters pour.
az A. Niagara throwing up clouds
Of EPrzT. that become a home Of
rsfub oTA II also occurs when the
SDse-rr- 10 tn a balloon or an aero
n
marion. the French astronomer, who
was very fond Of ballOoninE in his
younger days. once saw a circular
rainbow in that way. and curiously
enough = presented the appearance
Of an ordinary rainbow upside down
when cloSoB happened To hide ths
upper hAlf u IL.
Circular rainbOwT may also bs
-esu when the Eunligat ia reflected
rom the r1T1Ace Of smooth water.
because then the origin Of the rays
may be taken a. the point OF rrhsc-
ton. which would be below tho hor-
icon. tine bows being produced cor
FsgpondinG1T hiEh IN the air This
condition frequently occurs over the
basins OF waterfalls and often only
the under half OF me circle IL VIII
hle. producing the phenonenou q
rBInboE upside down. noticed BIZ
" F1amroH from his balloon
There are few more exquisite EIee-
INcles than THAI presented BY ths
inoSSEant playing and qufTsrinE Of
'heSe waterfall rain bows On . sSn~
shiny day.
The angles shove mentioned apply
only 20 the primary or principal
arch OF . rainbow. Often a Ds<-
ondary and fainter arch IL Ssea
outside the primary one. having an
extreme radius Of about - degrees.
By combinations Of eircSnEtaaoss
and conditions into which ] cannot
enter, groups q rainboWS are some
times seen, Sneh ~ the triple rain
bow IN which enc Of tie arches 10
formed ~ RuubNaNon rNHaefeS Nrop,
water, and this Grch intsrsects the