Evening star., 1899-03-04
THIS WABBLING WORLD.
The Scientists Have Now Found n
Twelfth Notion
From the London Standard.


From the London Standard
There is an interesting letter in Nature
this week on the subject OF the change OF
the polar axis. To talk of the twelfrh
movement OF the earth shows how far we
have wandered from the good old days Of
Ptolemaic astronomy when our globe Was
regarded as the center of the solar system.
We are. indeed. progressives, rotating about
an axis, whirlng round the sun, darttng
through space In the direction of the con-
stellation Hercules. emissaries from the un-
known into the unknown. IT is needless TO
enumerate all the eleven movements which
have been already discovered. but I'm addi-
ton to the three Just mentioned. there are
as many more which may have exercised
considerable influence on climate in the
long ages Of geological history One OF
these-perhaps the least important-is a va
Ration in the angle between the plane Of
the equator and that of the orbit about the
sun. This has the effect of increasing or
diminishing the tropical and polar regions
by Eearly three degrees. and of correspond
1ngly restricting or enlareing the temper
ate zones. That would probably produce
some effect upon the climate of different
places, but ii is not likely to be great. The
ether two movements combine results 30
which many scientific men have attached
great importance. The axis about which
itself in moving round the sun.
If the sky were a hollow sphere. and the
axis were prolonged. pencil fitted to its
end would trace out a circle round the
point, where a vertical line through the
sun met the sphere. But besides this the
orbit may be regarded as moving. 1t is as
though the earth were a top spinning along
a groove in a table round a lamp in the
center. and the table itself were slowly
turning These two movements have this
effect, that if the northern hemisphere is
nearest to the sun in the summer and
furtheSt from IL in the winter season. the
same will be true of the southern hemis-
rhere in about 1880 years and this alter
alton continues. How far this has affected
the earth in ages past is a matter of dis
pute, and the last word in the controversy
Has not yet been said. Biologists however,
have to deal with the fact that the earth's
climate has varied greatly in the long ages
of its history, and this fact requires eXpla-
nation.
At a period comparatively late the mean
temperature Of the Thames valley-to take
that as an eXample-may have been some
eighteen degrees lower than ii is at pres
ent. But at a yet earlier epoch IL must
have been at least as many degrees higher.
The site of London at one time might. so
to speak, have been in southern Greenland,
at another in northern Africa Is it pos
sfble that the earth may not always have
turned round the same axis?
If the poles wandered about the surface
of the globe, then place which is now in
the temperate zone might be brought at
one time within polar, at another within
equatorial, regions. This idea has found
favor. but mathematicians declare IL TO he
inadmissible. They admit that the poles
are not absolutely fixed. but affirm their
wanderings TO be so trivial as to be unim-
portant Sir John Evans, however, sug-
gested that if the earths interior was fluid
the solid outer shell might slide upon the
inner mass. The shape of the former
changes. for II is crumpled into ridges and
burrows and material is TranSfgrrad from
place to place. That may cause the shell
to move. and thus bring places into new
positions in regard to the poles. But here,
again, the mathematician stops the way
and says that even this could produce no
great change. Now, however, We are in
formed that a new kind of movement has
been discovered. The pole is said to shift
its position annually from fifteen to seven-
teen minutes. The statement in Nature is
founded on observations continued during
the last seven years. 1t seems strange.
however, that a movement of this kind,
which must affect the apparent positions of
the celestial bodies, has so long escaped
notice, and in any case 1t must be cumula-
tive to produce any real effect on climate.
AS the letter to which we refer points out,
change in the axis of rotation must af.
feet the relative level of sea and land That
it has changed is a commonplace, but the
latest and most distinct indications certain
ly do not admit of such an explanation. II
the announcement be correct, the fact is
interesting. but 1T is hardly likely to solve
the mystery of the past alterations of cfi-
mate on various parts of the earth's sur
face.