New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1892-02-06
SELECTIONS FROM THE MAIL.
A BIG WEATHER PREDICTION
PROFESSOR LEWIS SWIFT DISCUSSES THE = Fl
TEEN CLIMATIC CHANGES.

TO the Editor Of The Tribune
sir: Going the rounds OF the press is an article
under the above caption. written By one who appears
! 10 be unfamiliar with his subject. copy the foi
lowing extracts rs the basis of my criticisms. lie
saws: There have been fifteen climatic changes
since the beginning Of the glacial age. each change
lasting 10 500 years and each change reversing the
season I'm the two hemspheres the pole which had
enioyed continuous summer being doomed - undergo
perpetual winter for 1880 years and then passing
TO its former state for al equal term. kechoh'
ing these climatic changes in their order. we hau
entered the epoch OF moro genial temperature aooue
zoo WARS arc. we NAV reasonably expect
Gradual Modification OF our winters for 5000 years
to come. . There Is everything to snow
modification OF climate I'm our own days. II this goes
on In the future as in the past there will be marked
difference In the temperature 200 or 300 years from
now :"
Save that the season north and south OF the Equator
is reversed in 10000 years, the above excerpts
contain not a word OF truth. our winters instead OF
growing milder for 800 years past have been moro
severe since A. d. 1850, which time the earth was
in perheon mt the winter solscc, December IL IN
stead OF January 1, as at the present ume. Doing
nearest the In our winter and furthest tom II
In summer both the severity OF winters cold ana to
intensity OF summers heat are very slightly mitigaed
thereby q contrary effect being OF course produced
south OF the equator where before said the seasons
are the reverse OF ours But this, for two causes 70
be shown, will be reversed in about 1880 years Hom
A. d. 1850, or $500 years hence, when the earth
will be IN aphelon (furhest from e sum during our
northern winter which, at that time Will be snghiAy
| colder, and the heat Of summer VIII be some"hao
heightened state OF things that has obtained In the
southern hemisphere since the Mosaic creation
The eccentrclty or ellptcty OF tho earth's orbit,
which In our age Is slowly diminishing, Is about 1000
600 miles, and causes the earth TO be once in SIX
months 100000 miles more distant from the sun
than It was six months previous, but 100000 miles
when compared with 930OO,OOO miles the suns dis
lance IS almost an napprecabe quantity. THIS slow
decrease in the eptclty Of the earths orbit has been
In progress for ages and will continue about 3oOoo
years longer ut which time tho earths distance from
| tho viii be nearly the same during the chure
year. when the reversal OF the northern ard southern
seasons will When the clhpticty OF the orDio
reaches It's minimum, without, however, having arrVed
at perfect circle, it will change TO an increase, which,
after the lapse of many hundred centuries and the AZ
tannent OF It's maximum, again changes 10 decrease,
and thus will forever fuctuate between certain h4ei
values somewhat altering. in the course Oh the ages.
both intensity and length Of tho seasons at different
| and far parated epochs.
line through tho major axis, called the line Of the
apsdes, had position at right angles to the equl'
noctia line in 1850 when autumn and winter were OF
the same length though shorter than spring ana sum
MGR, which equal also since then no two seasons
are OF the length. At the present our winters
are shorter than summers for two reasons VIZ.
! First, the circumfeentlal portion Of the orbtaI
elpse IS shorter from the autumnal equinox u the
vernal than from the vernal to the autumnal.
| second, the earth being in perihelon in the former
case moves faster than in the latter and causes our
winters to be nearly eight days shorter than our sum
mcrs.
| Tho design Of this article IS not to explain the
OF the changes in the seasons, but rather 10 a.
count for their reversas widely separated epocis
| Ixtaa In nd1
the alteration of eptcity OF tho elrths orbit, rs out
lined above three causes may be adduced viz, change
in the oblquity Of the eclpc. tho revolution OF The
| earths orbit and the procession OF tho equnoxee
The influence OF the irstnamed Is slight that, for
the sake OF brevity, shall discuss only the effects
VI the latter two. Not only does the earth revoNc
from west east In It's orbit, but the orbit itself re
wolves in tho direction at the very SLOW rate o.
about 11."S5 annually. As every circle contains
! | ,200 oOo,, this number divided by 11.75 vii
| give the time Of complete revolution OF the major
axis of tho elliptic orbit, or 10000 years, which
| divided by two, equals % 900 years That Is u
| ,ay, the advantage VIC now possess OF belng IN
perihelion during winter would, because Of this
alone change the benefit OF the southern hemisphere
In 30 900 years when the earth would be In aphelon
during winter, which must, consequently, DC
slightly colder. Now, suppose the orbit 10 be
stationary, and that procession only produces the
change. IL Is universally known that the sun In his
apparent journey northward crosses the line about
the 10th OF March, but for not necessary 10 be
considered here his path touches at each successive
year "A POINT oO' ~ west or the crossing OF inc
previous one, and causes the sun TO arrive at the
crossing point equinox before he has made
complete revolution The time required TO complete
the circle Of the say l. found by dividing, as before
l,29dOoo' By 502i. or $500 years. hy thc
retrogradatlOn, therefore. OF The equinoctial point
| called procession Of the equinoXcs," tho vernal
e1ulnox would comp etc tie journey OF the earth
orbit In 2aooO years, or the reversal OF the seasons
north OF the equator would be accomplished By pre-
As however. the major aHls OF the earths orb u;
ii175. and the vernal equinox fctrosradcs so. "a
annually. they Of course approach each other
at a rate equal 10 tho sum OF both motios. about
62r. Dividing. ~ before. l,206,O0O- by 81 We get
nearly 81 900 years. In round numbers. therefore, We
hnd the seasons reversed In 10 500 years. I'M
Known writer has truhflly asserted But this reversal
| OF the seasons Is much too Insignificant cause to
produce IN any age glarial epoch or leo pefoh q
| phenomenon OF which neither the heavens nor the
! Tic assertion that the poles are alternately. for
periods Of 10000 years. merged In continuous summer
one. Each pole. regardless of any epoch has now ana
always will have its seasons. summer ana winter.
mentioned. a slight ntenslhcation OF the heat and cold
| OF the two seasons. That there will be a marked
| alteration OF temperature 200 or 300 years from now
Is too absurd Ia need refutaton. IL would DC inter
esting well instructive 10 learn IN WHAT nook or
conner OF the earth has been found the evidence OF
fifteen climatic changes since the glacial age, each OF
! IL. 500 years duration. ,
The investigations Of tie secular variations OF the
season, have tasAed the highest powers OF matle-
though periodic yet completed III cycles OK umc
| measured only by centuries.
| motions and the harmony and order with which the
mighty movements OF the universe are conducted under
them all wonderful display OF Infinite wisdom and
| power. ~ ioIlS sMit 70,