Year: 1876

Mountains have been explained by two
widely-different suppositions. One is that
they are due to sediments deposited
under water from the erosion of a wasting
continent which by upheaval have be-
come mountains. The other is that they
are due to uplifts, as the result of lateral
pressure caused by shrinkage of the earth's
interior.


Without attempting decision, we pro-
pose in this article only to state some of
the main points in the arguments pro and
con, and leave all to decide for themselves
as to which is the more reasonable.


We would naturally conclude that, if
mountains are due to lateral pressure,
they would be formed by the uplifts or
elevations Of the earth's crust. But this
is seldom the fact, for several reasons.
According to Prof Dana, many if not all
the mountains have their origin in the
bending down of the crust. As the crust
subsidized, the trough was kept full of
water, which continually deposited sed-
iment. This deposition about kept pace
with the rate of subsistence. In this man
ner many of our mountain ranges were,
in the earlier ages, taking the initiatory
steps in the process of mountaineering.
As the crust subsided and was covered
to great depth with an accumulation
Of eroded material, it would be weakened
by the earth's internal heat. An addi-
ton of several Thousand feet of sediment
to the surface would bring a given de-
gree of heat so many thousand feet nearer
the surface. This would often be suff-
Gent to soften or melt the sustaining
crust, which would then yield before the
lateral and vertical pressure combined
and cause the .crusts on the sides of the
trough to fold over and approach each
other above it, thus crushing the sedi-
mentary beds into narrower space, with
the necessary result of elevating the
crushed and folded strata in the middle.


The Appalachian chain illustrates the
fact that one mountain system may be
formed by several successive depressions
accompanied with the deposition of eroded
material. Prof. Hall attributes the cause
OF mountaineering to sedimeutary &C
cumulations, which, by their weight, are
sufficient to cause depression in the
crust Thus, by the addition of 10000
feet Of sediment the crust would sink the
same number of feet. Then, by a subse
quent elevation of the crust, the aecu
mulated strata would be raised into !.
mountain, independent Of lateral pressure
He Just reverses the idea of Dana, b.
making the subsidence a consequence 0
sedimentary accumulations, instead o
the accumulations q consequence OF sub
sidence. To this Dana objects, becaus
"the earth's crust would have to yielt
like film of rubber to have sunk a foo
for every added foot of accumulation owe
I its surface, and mountains would hav
] had no standing place."
q Another reason why the elevations du
1 to lateral pressure do not produce tn
high mountains appears in the fact that
when a series of strata is sharply ben
upward-forminga an anticlinal-theout
strata are fractured and strained apart
while the strata which are bent dowr
ward-forming a synclinalpresent t
the surface a firm and compact mas
This can be clearly shown by making


sudden bend in walking-stick. Th
hbers of the outer curve will be tor
asunder, leaving asplintered and ragge
surface, while on the inner curve the


will become unusually dense and firm


The fractured edges of the anticlin'


curve are in favorable condition to


Worn away by water, while the compa'


surtaceiof the synclinals, though formir


The valleys where the greatest amount


running water wonld act upon it, suffe


out little erosion. The consequence