Evening star. [volume] (Washington, D.C.) 1854-1972, 1882-12-28
Birth and Death Of worlds.

Prof. Proctor in Belgcavia.
1t has been shown that had past geol ogical
Changes in the earth taken place at the sam e
rate as those which are now in progress,
1000 600 of years at the very least wonld have
been required to produce those effects which
have actually been produced, we find, since the
earth's snrace was fit to be the abode Of life.
But recently it has been pointed out, correctly
In all probability, that under the greater tide
raising power of the moon in past ages, these
changes would have taken place more rap idly
AS, however, certainly 10000 600 of years, and
probably much longer time, must have elapsed
since the moon was at that favorable distance
for raising tides, we are by no means enabled, as
some well-meaning but mistaken persons have
imagined. to reduce the lfe-bearing stage of the
earth from duration of 100000, 600 of years to
minute traction of such a period. The short
life, but exceedingly lively one. which they de-
sire to see established by geological or astro-
nomical reasoning, never can be demonstrated
At the very least. we must assign 10000 600
years TO the lfe-bearing stage OF the earth's eX-
lstence II we now multiply this period by
seven Tor Jupiter we get a period of 60 600 600
years longer. But take the stage preceding that
OF life on the earth. From the researches of
Bischof into the cooling of masses of heated
rock. 1T seems to follow that period of more
than 3oO.OO 1000 years must have been required
for the cooling Of the earth from temperature
of 200Oo centigrade to one of 20Oo. a cooling
which has certainly taken place Sup
pose. however. that these experiments.
or the calculations based on them. were
Vltiated by some error SO considerable as to in
crease the real duration of the fiery stare of our
earth's history more than ten-fold the real
duration of that period being only 80 600 600
years. Multiply this in turn by Z, and we get
period of 210.OO0O00 years, or 1SO 600 600
years longer. We ought next to consider the
vvaporous stage; but the evidence on which to
form an opinion as to the duration of this
stage OF a planets history is too slight to be
the basis OF actual calculation. Here as Tyn-
dali has well remarked. conjecture must en-
tirely cease But by considering only two
stages-the fiery stage aud the bearing. or
rather that portion of the life-bearinr stage
through which the earth has hitherto passed
We ind the two mOnstrOus time differences
GOO aud COCO. coo. or $40 600 COO wears
In all. They mean that if our assumption as
to the effect OF Jupter's superior mass is cor
rect. then, supposing Jupiter and the earth
to nave started into existence as distinct orbs
at the same or nearly the same time, 24O 600 600
years must eapse before Jupiter will reach the
stage OF planetary life through which our earth
Is now passing. Whether the assumption be
correct or not. the time differences between the
stages of Jupter's life and the earth's are of
this order. They must be measured by tens of
millions if not by hundreds of millions of years
we must note, however, that the $40 900 600
years correspond with only. a seventh part of
that time in the earths history; so that we NAV
say that. ii our assumptions are correct Jupiter
would now be in the state i'm which our earth
was oi,UOo60o, years ago. or nearer the begin
nlng than the end of the fiery stage.