The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1879-11-28
PROFESSOR PARKHURsr's MATHEMATICAL EsrI-
MATES EXPLAINING WHY THE METEoRs

PROFESSOR PARKHURsrs MATHEMATICAL EsrI-
MATES EXPLAINING WHY THE MErEoRs
MIGHT NOT APPEAR.
To THE EDITOR THE HERALD
There are three reasons why should not conf
IDENTIFY expect to be able to the approaching
shower of meteors lend on" as suggested by Mr..
Proctor in the HERALD Of the 26th inst. First the
brightness of the moon; second. that the meteors
usually become visible after they enter our atmos-
phere, from their own combustion. and are so
small as to reflect very little light from tho
sun. whence we conclude that there must be
an immense number Of them within very small
field to make 1t possible to see them even
with the telescope; third. the anglo Of the
orbit tho meteors to the earth orbit s such that
the earth only be approximately In the line of
the train for few hours; and il the train should
then be near enough to reach us, before the earth
would have passed the point Of crossing, it would
probably be SO near that the Individual meteors
would be too scattered to be visible. A few compu-
ta&ions will show that in the absence Of the
moon. and with the telescope directed toward the
approaching train, the chances would be against its
being visible; although there remains, perhaps,
sufficient inducement for making the effort to OBJ
serve so interesting phenomenon this would be.
making visible the connection between the comets
and the meteors which astronomers have theoreti-
cally demonstrated to exist.
The angle between the orbit of the meteors ex-
pected tonight and that of the earth may be taken
for rough computation at forty degrees. We may
assume also that the custcr of meteors must be
braced within field Of not more than u degree in
diameter which would cover area four times as
large the moon in order to be distinguishable as
. nebulous body. Suppose the thickness of the
train to be TO- 900 miles, its distance from the earth
must be GOO 200 miles in order that it shall appear
no larger than degree in diameter. As the me-
teors and the earth are moving approximately In
the same direction these meteors would require
moro than twelve hours to overtske the earth,
during which time the earth would havo
moved not far from half million miles away from
scope could not possibly strike the earth and CON
sequently could not cause meteor slower. II we
assume the thickness Of the train be greater the
distance requisite to condense the whole into one
nebulous mass becomes proportionatey greater and
the difficulty is not diminished. II Pogson had
shower in 1872 (which he did not), the distance
would have been. perhaps, 1000, 900 miles. making
the thickness OF the train not more than 10000
miles, probably very much less while the earth
would have been at least 100000 miles from the
line OF the orbits so that instead OF seeing the train
"end on" it would have been Ut an angle Of about
forty-hve degrees.
These figures are all exceedingly crude estimates;
but it does not possible avoid the conclusion
be 1t would cover field large to be observed
with the telescope and would not be lend on"
but at such an angle Us would show the length Of
the passing train But If the earth should GROSS the
path in q portion nearly devoid of meteors, while
rich portion might possibly be seen as . nebulous
body, and should thus be enabled to predict the
shower for sOmesfuture return.
The condition OF the sky this evening suggests
fourth obstacle in the way of seeing the An
dromedes and that is the interpretation Of clouds.
Yet there has been sufficient space clear aroNnd
the radient point in its vicinity to make 1t GER
tain that we not now in the meteor stream. The
principal display in 1879 passed it's maximum.
taking into the difference Of longitude.
about three p. N. OF New YORK time; but we have
eighteen hours to make up for the three years
since leap year. which would bring the correspond
ing time about nine A. NJ. The shower may, there
fvre. not appear until after the HERALD goes to
press, and perhaps may appear late only to be
visible upon the Pacific coast.
HENRY NJ PARKHURsT.
BROOKLYN. Nov. ~, 1879. tial