The times. [volume] (Richmond, Va.) 1890-1903, 1891-06-23
tn. Futur, of the Dry Land.

Messrs. John Murray. Penck, Supan ana
De lilo, by the aid of the partogIaphie
documents accessible TO them. nave iQuhu
that the land relief may be represented by
uniform plateau rising 20 700 meters above
the level OF the seq. This plateau OF 600
meters is the object of incessant attacks ny
the ocean on one side aud atmospheric agents
on the otheE The rivers never cease carry
ing TO the sea the fine fragments OF the rocks
which the rain washes into them, after
they have been disintegrated by the
alternate actions of moisture and
drought, cold and heat, freezing and
thawing. BY the operation Of these clrcum-
stances sixteen cubic klometers are taken
from this mass every year. The continental
surfaces covering ll6 COO 900 square kilOmeters
we calculate that a waste Of sixteen cubic
Hlometers will remove each year layer
ll-lO0 of millimeter thick. The debris from
this LAYER will settle on the bottom OF the sea
and assume the form OF sedimentary deposits
they will take the place, then, OF CORE
spending quantity Of water, IN consequence
Of which the sea will rise 70 certain extent.
The ratio Of continental surface being 70 ,nd.
of the seas about as 100 10 262. the total result
will be a lowering Of the height OF the plateau
of about $4,000 Of millimeter every year
AS many times as this l50-lOOO OF MI III
meter is contained in 700 meters, or 1OO.OO0
mill,meters 80 many years will be required
TO bring about the disappearance OF the DRY
land. Make the calculation, supposing the
present intensity in the phenomena or ue-
structiOn % continue, and you Will hhd NAV
il will take A. 800 900 years 10 wear the surface
Of the earth entirely away. This may be re-
assuring figure to us. But the geOlogist who
looks az the past as well al the future tar
beyond existing generations can draw more
than one lesson from IT, First. the whole history
of the globe not being includedl III a space OF
time relatively so short, the result teaches us
that its equilibrium has more than once been
cd l.v,r nh GIsl0PQfl0n
too rare however. fOrit 20 be possible for man
10 have been q witness of them, which. build
ing up new Teefs as barriers 10 destruction.
have given new impulses 10 the action Of nat
ural forces On tho other hand, geological OBJ
servatiOns furnish tolerably approximate
measure Of the maximum thickness OF the
deposits that are made in the bottom OF the
sea. The total thickness amounts, according
TO Dana, 10 $4,000 meters. To learn
how long a time may have been
occupied with the formation of such deposits,
let us seek 10 represent 10 ourselves what now
becomes of the products Of the destruction OF
the continents These deposits. 1t ls now
known. do not extend, by agreat deal, overthe
whole surface Of the sea bottom; but they
form zone Of strata which the deep sea
sounding expeditions have enabled US TO de
fine fairly well. According to Mr. John MUIR
rays estimate. the sediments formed by the
destruction of the continents spread them
solves over about fifth of the oceanic sur
face. Thus, although the oceanic area IS
superior 10 the surface Of the land
the mass Of deposits distributing them
selves over only fraction of the extent, there
may result, at the end OF 100000 years. an
accumulation of sediments capable otforming
a body $50 meters thick. But this thickness
would certainly be very uneyenly distributed
almost null at the finishing point OF the de
posts in breadth its thickness would be
much greater near the coasts. and It would
not be hazardous 10 suppose that 1t might rise
there 10 1000 OF 5000 meters 10 realize the
total thickness of $4,000 meters-that is, 70
explain geological histOry-it would be sutfi-
cient TO suppose that the life of the globe
has included some fifteen or twenty periods OF
4.5OO 900 years or from 81 900 900 to 80 600 900
years, number little less than the 100 100000
years which Sir William Thompson has cal
culated upon estimates OF the loss OF internal
heat. Tue objection may he brought up that
| have neglected in this calculation the con-
tributiOns Of volcanic action TO the land re-
lief. which 1t is thought should be counted IN
attenuation Of the destructive effect OF run
ming waters We owe TO COrdler a calculation
that the layas which have been brown
I'D lduring the historical period repre-
sent at most 500 cubic klometers, OF, count
ing that period at 5000 years. a sixth Of
cubic kilometer per year. This is very little
affair compared with the amount OF the waste
which have pointed out. We should like
wise recollect that besides eruptions there are
also volcanic explosions like those which our
generation has witnessed at Krakatoa IN 1883,
Bangtaisom in 1887 and which our
fathers observed ut Temboro in 1882
If we reflect that the exploson of
Krakatoa threw sixteen cubic kometers
Of matter into the air. and that of Temboro
was still more considerable, we may be per-
mitted to say that volcanic action, instead Of
diminishing adds TO the constant degradation
of the continental relief l have not assumed
TO give precise figures on this subject. My
object Is less 10 exhibit numerical results than
TO present a view Of the relative magni-
tude of the effects under analysis. 1t
is evident that these effects can not
be neglected. and that they permit us
to assign 10 the geological history of our
globe duration less than the somewhat fan
tastic figures to which we have been occasion
ally asked TO give credit. II is nevertheless
true that the disappearance Of the continental
relief, while it may receive the attention Of the
geologist and thinker, is not one of those
events concerning which present generations
need trouble themselves. Neither our chill
dren nor our great-grandchidren will have "a
visible prospect of it presented to them as an
actual danger Translated for the Popular
Science Monthly from Cie ct TerIe.