New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1860-09-19

nearer tLan re va last July, AM not much more tA'
half the dstanee which will separate him from US IL
his opposition Of February, 1869. This looks ike
great rregulaIity how it comes abcut is easily under
stood.
The orbits Of all the plsnets elliP,ical, or elon
gated; some much more go than others. This elliptic
ity is known as eccerhicjty. Accordingly planet
orbit is more or less eccentric as it is more or less
elor gated Mar has the most eccentric orbit Of any
Of the great planets except Mercury though both are
surpassed in this respeet by of the asteroids.
The position Of tho is always toward one end OF
plsnets orbit at one Of the points called the fOci
Of the ellipse. Some notion of the place of these
points may he got by supposing circle to be drawn
cut, and its center measurable spot to be divided
into two halves half moving in one direction
along the line oTis Of eongston, the other in the
opposite direction. TIE longer and narrower the
figure is made the further apart these points, which
may be called the feel Of the resulting figure win be.
This explanation is lot meant TO give the law Of th
curves development but is only designed to ilustrat
the idea of elliptic centers of motion.
TIE point Of the planetary orbit nearest the focus
where the is placed is called the periheliOn, aud
TIE opposite tine dphelon, is well understood. If
the two orbits were circular and concentrc, the dis
and degree Of brightness of Mars would be the
came st every opposition If, indeed, though ellipsss
as they are tie eccentrciy of the two orbits the
sane the difference in the brightness Mars at different
oppositions, would still not be very marked, aud his
distance would be the same But when we consider
tie ecceuirciy of his orbit TO be far greater than that
of the earth il is in realty, the is altered
tally To get clear view of this interesting point
conceive 10 lie drawn plane before youthe table,
the foor for exampe-two similar ellipsss, ore
within the other to represent the orbits Of the earth
and Mars having the Gun in a common focus. The
lines joining the peTihelon and apheon points of the
two elpsts called the MAJOR ares will coincide. In
whatever part of their respective orbits the
epoch Of opposition occurs, the distance Of Mas
from the earth as vas just remarked, will be always
the same ard his brightness nearly Nor will this
depend upon the eccentrcty of the epses any further
than that the planet viii receive less light from the eur,
aud go lie less conspicuous the further his eccentric
path carries him away from that uminary. His disc,
though lees bright, will, however, always have the
same diameter. Now, LET the elpee drawn to repre-
sent the orbit Of Mars be elongated in the direction of
the msi axis, by having the apheion point drawn
aO ay while II perbeon point and the focus occupied
by the FUN remsiu as before 1t ia obvious now that
the earth aud Mans are never near each other as
epoch Of opposition they will be further aud further
apart az they approach their corresponding aphelon
points; and when both are in aphelion they will be
farther apart than at any other epoch Of oppostoni
and this 6iererce will be grs4ter in proportion as the
difference in eeeenIicy is greater is plain hatthe
chances aIe many to one tbst the two bodies will not
both he in peIiheon al any given epoch of opposition
This relative position wac closely appropriated at the
l.. NsfzA Nafh m lTa
closely still in the opposition OF September, 1871. In
August, l7l9 the same thing happened and Mars was
then 20 much brighter than usual as 10 excite consider
able alarm among the ignorant.
Professor Airy, Astronomer Royal of England,
pointed out some years ago the value of the present
opposition of Mars sfOTcng means OF determining
anew the distance Ct the sun from Or as 1t Is KNOWN
bis parallsx This defiance aud the resulting dmeh'
fons now assigned TO the solar system are based on the
results Of observations made on the last transit OF
Venus which occarred in 1863. Theaccuracy OF teSe
resuts requires confirmation, ard astronomers hau
Looked forward TO the next pair Of trdDsils oil venus
happening in 1874 and 1882, ss the nearest AID only
opportunity in this the next century for the complete
re- solution of The problem The great importance OF
this p,ot lem and the fact that with all possible care
as Professor Airy Observes the risk OF fetal failure 10
not nconsderabs led the Astronomer Royalto inquire
whether there were no other possible means of deter
mining the IaraIlsx. De hit upon Mara, and ingen-
iously showed how the opposiiOns of lo6O 1867 AID
1877 could be made TO answer the end in view
az well or better than the transits OF Venus
If the observations have Leen made the pres
ent year. according to the plan proposed,
some very interesting amour csments may be soon
looked for This will he the second great seryic, rem
dered by Mars 10 Astronomical science, TIE first being
the disclosure 10 Kepsr Il at the planet ny orbits are
not crces as they bad always been conedered to be
but eliraes ratber-a disclosure which was the inliia
spd necessary step in the emancipation Of Astronomical
scence from the gropDg empiricsm which, with cycles
and epic, cee Inc xtIcsble had ettered Ii from the very
teeinDing a enclosure extorted only after twenty
wears and more of most Encouraging, end vexaious
and unp1omispg, but Tremendously earnest ard deter
mined questioning. The past history OF the world vii
be summoned in vain TO chow any record OF laoo
mole heroic or a triumph more magnificent.
Mars has a closer family resemblance than any o he
planet T. the earth. Like the earth 1t is one OF IN
minor of the principal planets, having diameter 0
only about 100 miles, which gives il volume a0ou
one teu-,houfaudtb that OF Jupiter the Titan OF Tn
svste Like {! earth it fas day Of about II hours
and 8 wear Of about Cos Martial days lts year Il
diversified by stkrgly like ours, tncs the in
cinaton Of It's equator its orbit which gives rise
them, is only s. greater than is the case with the earth
The telescope directed upon it aud essduOusy employ
ed TO catch it's features dcoses upon s surface IRE
istble evidences of al atmosphere. Around the pole
dazzlingy white spots feen, wbe' increase IN IN
long Winter snd melt in ths long Summer OF that par
of the surface These Sir William Herschel contidere
80. atnd 90 mo 81
mers have sten no reason to question the sagaciy
the conjecture. This implies vapor in the atmospher
and water on the surface. Marked lineaments are nc
IL