Year: 1874

times bright, and that 1t would finally IL not hidden
by the SUMS rays be four times bright as at present
This computation makes allowance for the progress
sve increase accumulation of Brightness and as our
atmosphere is at o'clock in the afternoon
than at the brightness of the comet may be ex-
pected to exceed that given by the rigid computation


CoNcERNING THE COMETS TAIL.


On the 26th OF June 1 commenced computations with
regard to the comets tall Having no means at hand
OF reference to former comets, estimated the actual
increase in length TO be one-tenth each day. Subse
quent comparison Of the measures OF Donatfs comet
showed that its length about onetwelfh
each day. But this overestmate OF the increase is
compensated for by the statement OF Mr Hind that
June the tail nearly long as in my abundant
caution had assumed it to be Is days later. laid
down my planisphere series of dots representing
the positions Of the nucleus at intervals Of four days
TO July co. From the positions Of the Nucleus In space,


supposed for first approximation, straight lines TO
be drawn directly from the sum- Of the lengths severay
computed above stated and then computed the appa
rent positions OF the ends OF the tails which also laid
the panisphere Connecting these points gave
series Of lines, which marked g. b, c, d. on the
accompanying diagram copied from the original. the
first short line being omitted line joining the lower
extremtes OF the lines a, b, c. d, O. T. represents the
path which the nucleus OF the comet Will follow up to
July 2O and the lines themselves will represent approx
matey the position of the tail at the dates mentioned
and the letters for convenience. inserted the
table, 1t Is not easy TO describe the path OF the
among the stars because 1t has selected track
in which there conspicuous stars and although
II passes far from Polux, in the Twins 1t will be
after that star is completely lost in the twilight did
lay the panisphere the line for the tail Of
the comet on July 90 it passed off in the drec
ton Of Sirius aud, consequence OF the curvature OF
the tall knew this must DO incorrect. Not yet having
completed my revised computation ON the diagram
represent the tan following the same general drec
ton with the others.


CHANCES OF THE EARTH BEING ENyELoPED BY THE


TAIL


The result that reached in this preliminary computa


on the earth would be enyeloped within the tail
OF the 1t passed, was startling to me that
the question with regard to its publication The
chances were that either from erroneousiestmates
mistakes of calculation, the tail would pass the
earth without actually striking us; but on the other
hand there at least possibility OF its hitting us. In
the former the publication might create needless
alarm among the igDorant but 1t would tend to call
their attention TO the subject and TO enghten hem In
the case the panic which wonld arise when the
event became inevitable would be thousandfold
greater and there would be time to counteract it, I
the press Of this and other cities which has exten
syely copied from THE TRIBUNE my predictions, has
mixed them up with manifold errors and sensational
statements, 1t not my fault; ana your readers. at
least, Will do me justice


Among scientific expect the mere chance Of such





especially desrous that it should be actual contact
rather than approach for reasons, one OF which
will presently appear am especially gratifed. there
FORE that the tail should have been estimated last even
ing. by Prot Swift at eight degrees In length,
fairly above my published prediction.


Immediately after the publication of my first
ment, on June 80, commenced computations by the
formula given by Prof Perce. upon the theory stated
in THE TRIBUNE of the following day. My first impres
sion that certain particles OF matter having already
commenced their hyperbolic motion before June Q,
might, by following them in their paths, deter
mine approximately the length OF the tail at any
other period; but was met, first, with the theoretlc diff
hculty that unless there end TO that hyper
bolic motion the tails would increase in length indef
intely and next with the practical difficulty that the
tail was actually visible on June rs for but small part
Of the distance which the particles forming the taI
of June must hayo moved. Upon recurring to the
original computations OF Prof. Peirce, found that the
whole substance OF the splendid tail OF Dopats comet
early in October must have left the head OF that
within the last two weeks OF September, that at
least 100000 miles OF the tail had become invisible
Here is question OF philosophy. The particles
of matter forming the tail come from the head,
and must therefore be chemically OF the same
elements as the head. Then they begin TO act under
new law While IN the head they not acted upon
by the law of repuson, for the head moves independ-
emily OF any such law. They have taken condi-
ton, chemical, electrical otherwise, which has made
them subject to a law Of repulsion. Subsequently they
seem to be restored to their former condition. We do
not yet know what the condition OF the matter in the
comets tail We do not know whether IL is solid
or gaseous. II the former, and frcon with
the earths atmosphere would be likely to cause sueh
meteoric display as would aid very materially I'm sst
ting the question


EFFECT OF CoMETARY MATTER REACHING y,pru
1t was formerly supposed that II the head of comet
should strike the earth, it would destroy it, Modern
discoveries prove that such fears have NM
foundation. Less than two years ago the earth aetuav
struck by the head OF comet and probably verv
few Of your readers know It, and one Of us knew IL
at the ume It had been ascertalued that csr,.,n