New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1898-12-17
THE ORIGIN OF LAND FORMS.
HOW THE EARTHs SURFACE HAS BEEN
SHAPED.

EARTH SCULPTURE. On THE ORIGIN q
LAND FORMS BY Jam so 9ss,e Of "a deciosy ia
the University OF Edinbursn Ilus~a'ed' "e'
tavo. PIP. 39I. G. p Putnam 'e"s
SON Tor students OF Geography and Geoloek h
Ry, Israel c. Russeu Professor oiav Vd np az q
T. Putnams Sons t..'r I'D
These two works deahngsin a fasc'na''hs an.
authoritative way with the wonderfully Va''e.
surface Of the earth. are Complementary Va CAV
ether Professor Geikie who should not De con
founded with his elder brother. Sir Arch'oa'u
hut Is nevertheless a geologist or wide anu az. y
ra,e observation. touches Nightly on the asen0''f
tha, have wrought from without upon 'he io' :"
NJ the land and devotes himself chen! 10 ioi 'e'
that acted on the rock strata before the Proees'
Of weo,hering began Moreover. he taxes '"e
nhole globe under consideration. on the o'ne'
hand the American scholar confines his s'uus
IN his own continent and deals mainly WITH '"e
formation ana action of water courses
II must be remembered. at the outset OF an
investigation of this sort, that the earth q Us.
is made UP Of a great many layers soi''e ".
them soft limestones and :shales, ana soi"e VI
them lava or granite. one Is the accuh'uia.'o
at the bottom Of the sea OF material ''" ~
been eaten away by rain and wino from 'oi''
mountains and has been borne LOT NUM-. 80
n.rbons thousands. of miles thence to Its maj
restinc-place. Subsequent upheavais Oh '"e
ocean bed raise these deposits above sea leve''
ga hr,,g with them the fossil remains OF an IN
er;,a variety Of living organisms. Other strata
ho,o ei,bsr undergone strange transformations
% s,ruc.ure through igneous action. or else
hava baan noured out like fluid through vents IN
more solid walls.
When. therefore the denuding work OF 'he
storms and the brooks once begins. the eHec'
must DEPEND largely upon the chemical conpo-
s,,ion and hardness of the material on "hic"
the operate One kind Of rock VIII oislnteeia''
much more rapidly than another III the ioi"'e'
,s not entirely soluble at least its SOLUBLE por
tions will disappear and thus unlock particles
that pass off in the streams as SAND peooie' "
bo,ylders Othsr rocks scorn TO pctray 'iee
weakness OF their neighbors. and remain /"
monumental Isolation and dignity
Another important factor in the WORK OF snap
ing the earths surface is the disturbance OF
strata through the shrinkaee OF the siooe from
cooling II the wrinkles OF a baked apple are
mr., ran~oduced in every detail, at least the gen.
eral phenomenon is duplicated mus IL co'ies
about that In some parts Of the world the layers
Of rock remain almost horizontal one apo'e an
other 10 depth Of from one 10 nVe H'ies'
r.b4raos o7setvhere they Are folded UP into the
,,os, n,arv4uous convolutions And when, hav-
inc thesa differences Of material and situation
n deal with. the rain. wind and frost perform
their destructive functions. Of course the results
must vary greatly
4 good illustration Of comparatively undls-
turhed strata Is afforded along the Grand Can
Won II the Colorado Here one may see layer
above LAYER in q beautiful series cut down by
the river to a depth Of over mile. PROFESSOR
Geikie observes. however. that the vast plateau
through which the Colorado winds is not aoso-
lutely level. hut has slight tilt. Hence, strata
that are fully exposed in one region dip sradu-
ally until they are hidden thousands of feet be-
low the surface in another. l2O miles TO the
nor,heastward Nor should one suppose that
the erosive operations of the weather on TINS
plateau in past ages have been trifing. Aside
from the cutting out Of a channel below the
general level the elements have eaten away an
amount Of material that is equivalent TO layer
two miles deep over an area Of from $1,000 to
15031fsquare miles. mr.
A -Hommon yet interesting. phenomenon In
regions where the strata remain horizontal is
observed when a soft layer underlies hard
one. "a river having cut its way down through
both Of them, eats lateraiy into more tender
material. and leaves a shelf Of the other rock
overbangng the ravine. Finally the weight OF
the unsupported mass breaks off a portion. and
down it comes TO the foot Of the cliff. The
gradual recession of Niagara Falls and the
widening os the gorge below the cataract are
both due to this sort Of treatment The sea
operates in similar manner along the shores
Of continents ard islands. its action being con-
fined in many instances 10 soft underlying
rock, the higher strata although much harder
being conquered only by gravitation. The
lonely group Of the Farce Islands, lying about
halfway between Scotland and Iceland, are
the relies of what at one time must have been
considerable plateau. They extend over an
area about seventy miles in length. from north
70 south and nearly fifty miles in width Pro-
lessor Ceikie thinks that the plateau to which
they originally belonged must have had an ex-
tent Of fully $500 square miles
In studying the effects Of erosion in regions
where the strata are distinctly but slightly In
clined. it IS necessary To distinguish between
those cases in which the stream follows the
direction Of the dip" and those wherein it runs
az right angles thereto In the former case the
sides Of the excavation are likely to be alike
both Of them nearly quite vertical The
planes Of cleavage. or the "joint planes" will
be run perpendicularly, and hence the faces left
cS the sPhtting rock VIII be so. too. But when
the river runs across the direction OF the dip
the Joint planes VIII be inclined. and on one
side az the stream they will lean away from and
on the other lean toward the water-course.
The Consequence viii be that the side where
these planes recede as they rise from the bed
Of the river nearly vertical cliff will remain.
on the other-straneely. perhaps-a series of
steps, constituting very gentle slope. will be
formed. Consequently. the two sides OF the val
ley will present very dissmar aspects
When succession Of rather sharp foldnes
have occurred side by side. disintegration Is apt
10 go on more rapidly on the crests Of the
ridges than in the hoows between them And
II often happens that at the very top Of one Of
these uplifts several layers Will be eaten
through. and sfratlra win he -e,..oso.a -.