Evening star., 1908-01-19

| of the air at great attitudes over the
northern hemisphere has generally been
supposed for some time. But Prof Trow-
bridge finds that while there is a drift
predominating toward the cast, 1T may be
/ in any direction at attitudes from fifty to
sixty-five miles up This is so over north
eTn United States and England, and pc
! hapS over the entire north temperate zone.
/ This discovery that air currents may rush
1 in any direction at these great attitudes
! is an important fact bearing on the cir
culation of our atmosphere. 1t is cur ous
| fact that none of the night meteor rains
showed a westward drift. while nearly
all those seen at daylight We're going
Westward-opposite to the predominant df-
rection of the night trains. This west
ward drift of the day trairs-which We're
the Iower-took place in most cases prob
ably below fifty m les. Thus these OBJ
serya tions give almost conclusive evidence
that the upper atmosphere is composed OF
currents of different velocities o-e above
the other In atmosphere zones from
five to ten miles deep adjacent currents
are usually in different directions: but IN
some cases there will be, in one zone. Al
most calm. directly above or below
which there viii be a current of consid-
cradle velocity.
Zigzag Meteor Trains.
In these meteor trains there are some
times several bends. which give them the
appearance of MS" or ms" in Ire
sky. their straight lines being miles II
extent These curious zigzags, accord
ing to Prof. Trowbridge. result from Varl-
aticns i'm the velocity or direction OF ar
currents in the different attitudes covered
by the trains. In other Words. IN sucHi
instances. meteor train mas crosseu
number of supermposed strata OF ar
moving in different directions, with Varl-
Gus velocities. sIe thinks 1t probable thdt
up to sixty miles there are gradients oi
pressure and hence unstable conditiohS
such as accompany storms near the sur
face of the earth. Positions of the con-
tinents and oceans below seem TO govern
the prenominating directions OF even Tue
upper drifts. Passing northward through
the north temperate zone. me preooih'
mating upper currents appear to be nfst
northward then northeastward and Mai
ly southeastward. when latitude fifty de-
grees to sixty degrees Is reacheo
The most remarkable meteor train taken
into account by Prof. Trowbridge re-
mained visible for fortp-four minutes. II
was thirty miles long. a mile wide and
occupied zone between forty-nlne ana
fifty-nine miles above the earth. At hrst
Il was hayonet shaped. and. although very
distinct stars could be seen through II.
Four mintes later it was stretched out
nearly horizontal. but with right end
hooked up and left end similarly bept
down Later it spread out into straight.
horizontal line. tapering at the ends This
mysterious body after thus sluggishly un-
bending in space for three-quarters of an
hour gradually faded from view.
Downward movements Of meteor trains
are due to falling air currents rather than
to gravity. in the professor opinion.
Gravity seems not to affect them. In
fact, only one of long duration has been
noted 10 move downward at all. Some
astronomers regard these bodies as made
up of fine meteoric dust. but Prof Irow-
bridge says that ii is safe TO regard them
as clouds of gas or vapor whose positions
and shapes change with the drift OF the
upper air. Those seen at night are far
too bright to be due t. Effected light.
Hence he regards them as self-luminous,
or shining by their own light, as is indi-
Gated also by their spectrum.
That they are due to gas phosphoreS-
cence he thinks most likely. He is engaged
upon experiments to determine If they
due to the same phenomenon the
''afterglow produced in vacuum tube
by electric discharges. III. suggests a sys-
tematic survey of meteor trains by OBJ
servator:es wnere nightly watches should
be kept during the seasons of meteoric
showers Wherever there are two OBJ
separated by a good base line
such forms can be measured by triangula-
ton. A small telescope for noting the
drift among the stars would. he says,
be tine only instrument required.
JOHN ELFRETH WATKINS. :