Year: 1874

Professor Henry NJ. Parkhurst has writ
ten a second letter to the New York Tri-
bune, regarding the comet, which we give
below. 1t is comforting TO learn that the
monsters tail will keep some millions of
miles from the earth, and that it is travel
ing 5000 times faster than an express train:


Since writing my communication in the
Tribune of July 4, have satisfied myself
that the delay Of the comets tail from curv-
ature will be about four days, during which
time the earth will have moved 80 far that
no probable errors of computation or of
estimation would bring us within it. Hav-
ing settled that point, L shall introduce an
Illustration which otherwise might have
been too suggestive Of danger. A tall man,
having an India rubber club, two feet long,
and three inches in diameter at the end,
sees spider running very rapidly across
length and brings it down with a
terrific blow. He aims for point two
feet in advance of the spider, so as
to allow for it's motion, and strikes very
nearly the point which the spider would
have reached when the club struck the
table; but in consequence Of the club bend
ing little more than he anticipated, the
spider escapes by one inch. This is an ap-
proximate representation, on a small scale,
/
three weeks, with two exceptions. In the
| first place the club, instead of being of rub
ber, is of such attenuated material that if
| the spider were hit he would not know it;
| and secondly, an ordinary spider would be
many thousand times too large to represent
the earth. Perhaps 1 should add third,
that the size of the club is only known from
estimates. since it may increase in thickness
during the blow.


| On July estimated the length of the
| tail of the comet to be 70 3V, but the end of
| it was so faint that many persons saw it
not much more than half that distance. On
July estimated the length to be 12o, and a
| company of persons with me varied in their
estimates from l2o to 14o by comparison
with stars known to me, and one, "by the
aid of little Imagination could see it for
alength of l4o. Taking my own estimates,
the tail had increased in length sixty per
cent within these two days, although part
of this may be due to the unnoticed haze in
the atmosphere on the third.


The brightness of the comet on the third
and fourth indicates that ie will have an
equality on July IA with the star Affair,
the brightest star, with three exceptions,
visible in the evening with it. As Donati's
comet equaled Arcturus in brightness. am
by no means confident that the present will
be equally bright.


The motion Of the earth is $50, 900 miles
per day; that of the comet about 1900, 900
per day, and will continue about the same
so long as it remains visible. The motion
of that part Of the tail nearest us is nearly
100000 miles per day; that is, seventy
per second, which Is 5000 times faster than
the motion Of an express train. The thick
ness of the tail assume at about 5000, OOO
miles at the distance of 26,O0O0OO miles
from the head, when it shall have
reached that length. If the earth were
to pass centrally through it the pass
age would occupy about twenty-four
hours. Passing through the extreme
edge, as l at first thought possible, would
not occupy more than four to six hours
NV computations indicate that the nearest
approach to the centre of the tail will be
not less than 100000 miles, which would
be distance from the edge of the tail Of
100000 miles, which is six times the dis
tance of the moon. But this will be sufi
ciently near to cause it to appear enor
mously large, if it can be seen at all, o.
which hope to be able to speak more defin
itely within a few days. One thing is GER
tain; it will be there whether we can see il
| or not.