The New York herald., 1874-11-30
Figy. s

the letter represents venus approaching the
nrst stage OF her transit, and apparently distant
from the sun by space equal to her own breadth
before the embarrassing band appears. The inter:
vening lines are exceedingly fine threads 50 fitted
In the telescope to run along the rim OF the
IN such way that the parallel line 80 the right
lines is previously fixed with perfect accuracy.
AS Venus advances, the observer oscillates the
lines up and down until the planet attains the
position Indicated in the diagram, Just touching
simultaneously the lett hand line LIS and the
cross cross line Ins instant s the stage at
when she touches the same circle at her esress
| In tnis way her contact with the dotted
circle might be found before the obstacle alluded
| to could Intervene, because the blur does not
| two-thirds OF It's own diameter from the sun.
This method would not interfere with the existing
meter used by the astronomers, but would differ
from the present method lnasmuch as the pas
sage line OF the planet would be measured across
not across The sun merely. The diagram shows
only the external contact with the dotted circle,
but from wha: has been said II can be stood
how, with additional parallel threads, internal
contact with such an imaginary circle could
be signalied.
Long after HALEY had propounded his plans for
metod wherehy the nrohIem could he soivsI
another mode, lar simpler and more beautiful than
his. was proposed before the transits OF l76l ana
1859 by DellSle, q celebrated astronomer.
For the sake OF clearness In the description
thereof we Will conceive the sun to be condensed
lutO du luLcuscIy StAIs bHOOtluk MS
beams toward the earth like a binding calcium
light. When Venus begins her transit she will
se earth as Venus rolls Between us
track the planets transit would occur under pre-.
On the disc Of the sun: The same
line parallel to this track. These lines would
run nearly east and west. TWO distant stations,
nlAnef
shadow VIII first pass over the eastern station,
then ny westward along the ground with extraor-
binary rapidity, reaching the western station In
very few minutes. The number OF minutes and sec
onds consumed during the westward journey OF the
the solution Of the problem. according to the
method OF Delisle. In fig. the outline OF this
Ran Is ne m Is 70 De
upon the north pole and the northern hemisphere
Of the earth, Venus and the sun being also IN
view. The eastern station is at A. the western
instant at which ne sees the planet passing be-
tween him and the SUMS centre. Venus moves
onward until she reaches the position w. passing
directly between the sun aud the observer at u.
This moment is similarly recorded by the astrono
pianets shadow passes A 1t will be found 10
arrive at IN about ten minutes aiterward
Hence 1t would travel $3.50 miles IN ten minutes.
Now the velocity or shadow depends upon the
velocity OF the object that casts 1t; moreover, II
luminous centre the swiftness OF the shadow Is
double tnat OF the object, and so on. We know by
kepler'S law tnhb JUe edTtnS Instance from the
sun is ten n.seyenths OF that OF Venus, and,
travels with ten-sevenths as much velocity
as Venus herself Consequently, the $3.50
IN is ten mnutes % is ten-seyenths OF the distance
traversed by Venus herself IN the same time.
Venus must, therefore, In ten minutes have rushed
over distance Of 1910 miles. The reader may
now ask now 1t is possible that Venus only goes
at the commencement OF this article, she traverses
space at the rate OF 200 miles per hour. whence
tins apparent discrepancy IL must b, borne in
MUD that while II IS quite true that she courses
round IN ner orbit with this latter velocity, the
earth Is performing similar onward movement In
It's own orbit at the rate OF l,l00 miles minute
Both bodies are consequently rushing around like
two chargers on q circular race track, the inner
horse outrunnng the other. as does Venus with
tne earth dIl; Inc n,s,ance a,s4o miles Is
Venus ouistrips the earth in ten minutes.
And so Will the planet continue to gain upon the
earth, until at length (after the expiration OF 5s4
days. 1t will have beaten us out by a distance
equal to the length OF its own track for AZ the end
OF that time 1T VIII bave circied around and come
up with US again, as has been determined from op-
servations OF her movements among the stars. II,
then, in ten minutes Venus outstrips the earth
4,940 miles, In an hour she would distance 1t 2e $40
mites, in day twenty-four times this amount aud
In 5s4 days about, ZOO, 600 miles, which Is con-
sequently the length or her orpit Venus Ike
the inner and swilter steed on the race course,
passes us by on the sth OF December,
and steadily gains at . rapid pace, 30 that
eventually she performs two aud tnree-nfths Jour-
one and three-hfths circuits IN the same time-5s4
Gays. In this period she makes one revolution
t1 the sse ssen y Ups
itse into this shape: III Venus outstrips the earth
20. 400 miles In hour what must be the length OF
her oroit or the distance oy wnich she outruns IL
In 5s4 daysY In order to avoid somnferous COM
phcations we nave omitted one important fact IN
the above calculation While the shadow OF
station ut Is being carried eastward by the
revolution OF the earth on It's own axis, with .