New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1874-07-09
GROWTH AND DIRECTION OF THE COMETS
TAIL.


AN EXPLANATION OF TIE RELATIVE MOTIONS OF
THE EARTH AND THE COMET AND THE EXTFN-
SION OF THE COMETS TAII-RFPLY 70 THE
CRITICISM on PREVIOUS COMPUTATIONS.
To the + dttOr Of The Trt5Une.
SIR: did not receive until yesterday the
clements and ephemeris Of Dr. neiien, derived from
observations extending over period of one month.
Comparison with the position OF the comet last evening
proved it 10 be about 40 norhward Of the predicted
place, and within about 1 Of the place computed from
my own orbit. think may safely say that the comet
will pass it's pcriheon tomorrow Thursday morning
O'Clock July s, Gas NJ T. Washington as
Economical tmel As DOnatis comet developed "a brit
ancy 80 times greater than that computed from the
established formula, should not be at all surprised II
this comet notwithstanding s dmncss for the last two
nights. should equal it within the next six days.
As l do not consider myself responsible for anything
which is not published my own signature IN The
TRIBUNE. l not thought 1t necessary TO correct
misrepresentation Of my opinions even the language
imputed in other papers. But hope always to be
ready to when pointed out and TO
explain apparent discrepancies in my statements | do
know that can better reply 20 your correspondent
Mr. A. p. sprague, IN THE TRIBUNE Of this morning
than by definite explanation than have hitherto
gwen the motion of the particles forming the comets
tail; and 1 shall try 10 illustrate IL by diagram as
accurately representing what suppose to be the true
conditions as consistent with perspicuy. The earhs
OrDt being inclined at angle OF Geo, crossing the
plane of the comets orbit is foreshorened into a narrow
ehpse axis OF which is the line of nodes
Ii is because comet will pass between w. aud the sun
SO nearly node that the tail Will approach so near
us Had Venus "a tail 3O0OOOO0 miles long extending
directly from the SUM- 1t would envelop the earth on
Dec g. at the time Of the transit and in consequence OF
the transit.
The particles which leave the head OF the comet on
July T. at A. ire carried forward by their momentum
ana away the by its excess Of repusiye force
and 20 days tins repusye force will carry them TO
the equal 10 that OF the earth, while
the momentum viii carry them forward, not only
550O0CO miles, the distance from the earth the 4h
but about 3OO00OJO miles more the distance which the
earth will move in the 20 days. Since the momentum
carries along the heaG of tho and all intermediate
points Of the tail about the distance the actual
length OF tue tail on the oath depends almost wholly
upon the OF the repaslou for 1t evident that
if the repulsion the particle out only
half FAR, the momentum being the same that portion
Of the tail would be only half long 1t is not force
derived from head Of the comet which their
motion. Whatever force may be derived is small
that II is entirely neglected in these computations. 1t
proper TO remark thai, although IN tho drawiul to
prevent confusion have been obliged to represent the
orbits OF the particles composing the tail
ward the SUM- matter OF fact they convex to-
ward that luuinary.
The calculation from which M sprague derives APP
Gpon the idea the OF particles IL
to be computed by dividing the distance, f. instead OF
tie distance AZ, by the elapsed time. Incidentally Will
explain expression passing through the tail of
"A comet 26 c0 mile. from the head" seems d have
been misunderstood that hoped that July "a the
tai would be than twice that length. but that
whatever length that would be o,iou with re-
gard to IT, This is illustrated in the drawing by the cx
tension Of the tail corresponding To each fourth DAY
beyond the representing the orbit of par
cles leaving the head on July 4.
AZ matter Of scientific accuracy desire TO make a
correction with regard 10 the rate OF motion OF the
comets tail assumed, for convenience that the tail
would move with velocity nearly correspondent with
required by the old theorystha the tail points
directly from the Upon examination Of my com
putatious the hyperbOe theory find that motion
is not much more than half Of that, which would be
only $500 times fast express train this j.
twice as rapidly Mr. sprague assumes 1t move iu
order 10 reach the result that the tail VIII reach Il,
before the middle Of August HENRY NJ PARRHURsr
NGo YOrk, July s. 1874.