The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1867-08-03
ASTRONOMICAL.
u.,.o,,. showors-DispIay Expected In
August. ...

AeteOTtc ShOWoAs -
August
Tu,o to,lowine communication is published in
ahe Boston Transcrp =
T,,o nnblic excitement over the magnificent
-oeteoric display of last year has not, perhaps,
so completely evapoTated as 10 denude the ex-
,octe5 shower of the coming August of all in
kerest 10 the popular mind. IL Is needtul, how.
ever. to give warning that this exhibition will be
tame compared with that seen last Novem Der on
the other side of the Atlantic. The August and
November meteors belong to independent
streams, and il could only be by most remark
able coincidence that the August shower OF TINS
wear should be very different IN character from
The usual run of such appearances. IN iact, II
The reader on the evenings OF the 9Th and 10th
of August should succeed in counting shoOtlng
stars at a greater rate than three or Iour
minute for any length OF time, ne may retiFe 10
rest with the confident assurance that he has
Titnpssed a very satisfactory and unusual dis
plRy; for, though its recurrence is more regular
md certain. the brilliancy of the August shower
bas Of late years at least, been inferior to that
OF November. ,... -.... -. IL
Ainct from the sporadial, has been known for
more than q century. Muschenrock, IN lf6Z,
6rst called attention to the great abundance of
meteors during the month OF August. Quetelet,
Olbers AID Benzenberg aiterward nailed the
matter more closely by the discovery that the
maximum number occurred on the nights OF
the 9th and 10th of the month. The latter date
being st. Lawrence's Day, this shower has been
famlIiarly known as the Lawrentlus period.
The Chinese and other ancient records supply
accounts of great showers of shooting stars eVl-
dently belonging to the August stream, In the
following years of the present era:-Sll, 800,
s24, $50, $685. s35, SAL, 924, 025, 926 933, 1929,
l243, l45l, 1879, 1854 1888. From these the
astronomer Schlaparelli, who has Of late made
some valuable contributions to meteOric theory,
6nds what be thinks evidence that this stream
Of meteors has a period of revolution OF los
years. This, however, is uncertain, and cannot
as yet take its place among the recognized and
indubitable facts of science.
II will doubtless be remembered that the me-
teoTs of the 18th of November appeared to ema-
nate from point of the constellation Leo, in
part OF it commonly known as the Sickle. This
apparent divergence of the meteOrs from one
point of the heavens-the necessary perspective
eject of paths which, for the small space of time
occupied by the earth ia passing through the
ring, are nearly rectilinear and paTallel-obtalns
also in the case OF the August meteors. This
point must, of course depend upon the direction
in which the earth is moving at the time of the
shower, and also the inclination of the ecliptiC
of the plane in which the meteors revolve. The
radiant point for the shooting stars OF the 9th
and 10th of August is actually found to be be-
meath the sWord-arm of PeTSeltS, between the
constellation of that name and Cdn1eLOpdrddius
There are also. it is thought, indications of three
other radants tor the same nights, OF which two
are said to be in DrGCO, and the third near the
North Pole. Ii these are TO be depended upon,
it would seem that there are several streams
having a common node and inclined at different
angles to the plane of the terrestrial orbit, and
into which the earth plunges at the same time.
1t will then be matter OF great interest for OBJ
servers 10 determine on the nights in question
whether the apparent paths described by the
meteors, when traced back indicate more than
one source of emanation.
One item regarding the Lawrentius meteors
very worthy ofnotiCe is that the earths encoun-
ter with them takes place later and later in the
year at each successive annual revolution.
During the ninth century 1t occurred about July
20; in the thirteenth century on or about August
2; In the fifteenth century on August 7. 1t now
happens nearly three weeks later than it did
one thousand years ago, which is as far back as
our accounts extend. This phenomenon is
reierable to the influence eXerted by the larger
planets OF our system in disturbing the position
OF the meteor ring, and thus changing the point
OF intersection with the terrestrial orbit. This
shifting OF the point of intersection along the
earth's orbit, which astronomers have desig-
mated the secular variation of the node though
lmperceptible from year TO year, becomes very
notable in the march of centuries,
A motion OF the node analogous to this has
also been found 20 exist in the November ring;
IN which case, indeed, its amount has lately fur
nlshed valuable criterion as to which is the
true of five possible periods of revolution of the
ring. This element of the model variation may
at some time, perform for us a similar service
In the determination of the period of the August
meteOTs,