Year: 1865

BY drawing a line from the top OF
Table Mound, four miles west of Du-
buque, to the top of the Sinsinawa
Mound, six miles east of the Mississip.
pi river, we find that it is elevated
above Main street six hundred feet,
and above the residences on the bluffs
four hundred feet. This line in one
era of the history of our globe mark
ed the surface of the country. All
that portion of the strata from that
line down to the level of the prairies,
and bed of the Mississippi river, has
been abraded and washed away to
form the table lands and valley through
which the river flows. Where the city
Of Dubuque now stands is six hundred
feet below what was once the surface
of the country, and the questions may
be asked, where has this vast amount
of sedimentary matter gone ? and for
what cause was it necessary that il
should be removed? In answer to the
first question it may be said, that if
six hundred feet of rock had been
abradcd to form the valley of the Mis-.
sissippi at this point, and three hun
dred feet taken from the level of the
prairies back of town and on the Wis
consin side-that the same line may
be extended from the Sinsinawa Mound
to the Platte, Scales, Sherrill's and the
Blue Mounds, which are from twenty
to forty miles distant, and the same
amount of rock has been taken away,
and we have evidence that the same
amount of strata has been removed
South for hundreds of miles along the
line of the Mississippi river. In an
swer to the second question it will be
seen that this part of our continent
was at one era fiat table of rock -
none of the valleys, ridges, mounds
and vertical walls of limestone, which
are now seen about Dubuque, had yet
an existence-it was the action of elc-
waiting and abrading forces which took
hold of this tabular strata, as the
sculptor takes hold of the solid block
of marble, and have modelled and
worked out the perfection of country
which we now behold. Had it not
been for the forming of these valleys
and ridges we should have had no riv.
er system, no drainage system, nc
spring system, nor elements in the
soils, to have grown wheat and corn,
and sustained population. BY tax.
ing look ut what is known as Fan.
nig's quarry, opposite the city and
near the level of the river, we shall
see great blocks of blue limestone
quarried out from nearly horizontal
strata. On examining this rock we
find it made up of millions of fossil
shells, that, at what is known as the
Silurian age Of our globe, were filled
with animal life, and swarmed on this
level, the bottom of an ocean. We
are now six hundred feet below oul
line, and are treading what was once
the floor of the ocean, and for six hun
dred feet above our heads, atom by at
ON was piled the same limestones
which have been removed to form this
valley.


In attempting to comprehend intelli
gently these causes and effects, We
must remember that what are now be
ing described as phenomena connect
ed with strata and abrading forces il
the central part of a continent, ant
the laws connected with the marking
out and abrading river systems, have
here been acted on a scale of vas


magnitude, as compared to those O
the ocean slopes or smaller basins o
the continent, and that it is only b,
comprehending these forces working
upon this scale of grandeur that VIZ
shall be able intelligently TO compre
hend the facts named. Our contimen
has natural divisions. The Atlantic
slope being all that country east o
the Alleghanies reaching from Main,
to Alabama and sloping toward tn,
Atlantic, the Pacific slope being tn,
country west of the Sierra Nevada
and sloping toward the Pacific, the ia
bic lands of Utah, Colorado, and Idaho
being the country between the Sierr;
Nevada and eastern range of the Rock,
Mountains or Great Andes Of our con
tinent the basin of our lakes beins
the country sloping towards the grea
chain of laSes, and centrally situate,
between these the great Valley of tn,
mississippi, or basin of the continent


Each of these natural divisions of TIN


continent has its river system, ridg


system and mineral system. The ba
sin Of the continent is formed of tn