The Iowa plain dealer. [volume] (New Oregon, Howard County, Iowa) 1867-1895, 1884-07-31
Where Did Life Ecgin .

Regarding the earth, then, rs Mt one
time mn intensely hot globe, totally des
titnte OF organic life. one OF the prin-
cipal and indispensable conditions oil
rendering it habitablc for plants md
animals evidently would be the ra,;ia-
ton into space of its excessive and d.
strsetlse heat. The accomplishment
Of this, with the train OF concurrent
effects which would follow, or ut least
ever have followed the gradual rednc-
tlon Of temperature, is all that would
be necessary to render the earth SUIT
able place for the maintenance of veg
etable and animal life. At any rate
this is precisely what has taken place
since tine commencement of the Azo;c
age, and is still taking place on parts
of the earth's surface to-day, visible
ard obvious to any observer.
Our inquiry, therefore, is reduced to
this question: What part or parts of
the earth's surface first became suifi-
GENTLY cooled by radiation to be habit
able by plants and animals?
A supposed case may help rs in
reaching correct answer to this ques-
tion. Let us assume, then, the earth,
at the time it was molten mass, had
been and was revolving in an orbit SO
near the sun that the amount Of heat it
would have heen receiving from the
sun would have just equali1ed the
amount of heat il was losing by radia-
ton. Under these conditions it would
have cooled as the sun cooled--neither
faster nor slower. This helps MS to
lok 4, xr<
the sun is, and ever has been, on offset,
so far as it goes, to the heat lost from
the earth by radiation. A statement
of the loss of heat from the earth dur
ing any definite time may be formulated
in this way: From the heat lost from
the earth by radiation during given
period, subtract the heat received by
the earth from the sun during the same
period, and the remainder will be the
net or actual loss of heat. Sidereal
heat received by the earth being intinit-
esimal in comparison, is not here taken
into calculation. But We're it more
considerable, it would not be important
in this connection, for it falls on all
parts of the earth about equally.
1t is evident, from the present con-
| dition of the earth's surface, that at
the time it was a molten mass, and for
| long time thereafter, it radiated heat
into space much more rapidly than it
received heat from the sun; but, nev-
theless, the heat Of the sun is, and al
ways has been, offsetting the loss oi
heat from the earth by radiation to the
full extent of the heat which the earth
had been receiving from the sun during
| the time.
But this snn-heat, this offset to radi.
alton, has not been received by all parts
of the earth equally. The equatorial
belt, or torrid zone, has always received
the most per square foot, or in proper
tion to its area. The two intermediate
or temperate zones, have received the
next largest amount per square foot, OF
in proportion to their area; while the
polar, or frigid zones, have received
the least per square foot, or i'll proper
tion to their area. Ii the amount O.
sun-heat received at the equator be
rated at 1000, then, uaon the same
basis, the average sur-heat Throughout
| the torrid zone should he rated at 975
the average sun-heat throughout tn,
temperate zones at 7o7, and the aver
age sun-heat throughout the fliglt
zones at I54. or less than one-half tina
of the torrid, and less than two-third.
that of the temperate zones. We speal
here, and shall hereafter, of the geo
graphical zones Of the earth for th'
sake of convenience.
The greatest amount Of heat receivet
from the sun and otisetting radiation
from the earth, other things bein,
equal, is, of course, as we have seen a
the equator, and less and less every de
gree north and south Of this line to TIN
poles. II, then, the frigid zones hav'
been during al this time receiving tn,
least heat from the sun-the least of
set to their own loss Of heat by radi
ation-does it not follow that they Wer
the first parts Of the earth sufficient,
cooled to maintain vegetable and ami
NAL life? The inference seems inev
itable.-Popitiar Science Monthly.