Semi-weekly south Kentuckian. [volume] (Hopkinsville, Ky.) 1883-1889, 1888-09-14
THE GREAT LAKES.
Geological History of Their Formation and
E. Change In Their Level,

| thhhBe Lover.
Promising that lakes are DESTROYED
by rivers, by the double process OF
filling them up with sediment and
OF deepening the channel of escape,
and that, on the other hand, lakes. are
formed chiefly by the upheaval of the
earth's surface and by its erosion by
the movements OF glaciers, the author
devotes the greater part OF his article
to the geologic history OF the forma-
tion OF the great lakes. Their beds,
with the possible exception of Erie,
were secured out of solid rock by
the great glaciers of the ice age, but
accumulation of debris in many cases
increase their depth and influence tho
direction of their outflow. The removal
OF this debris, in the case OF the
Erie, for instance, would reduce it
greatly, perhaps entirely drain it, and
would make it flow into Ontario and
Hamilton. The increase OF heat caused
the edge OF the great glacier TO retract
from the southern border at Fort
| wayne, where the water generated
upon 1t flowed into the Wabash, and
separated Erie and Ontario into two
lakes. But as long as the ice remained
In the st. Lawrence valley the waters
found their escape into the Mohawk at
Rome. One of the beaches formed by
the action OF the waves has its crest
marked by the ridge road from Lewis
ton to Sodus. At this time Lake Erie
was only one-third as long as now, and
its surface was only one-fifth as great,
Toledo, Cleveland and the Bass Islands
being far inland. When Lake Ontario
forced new output through the st.
Lawrence valley its level was drawn
down five hundred feet and its area
reduced ninety per cent, becom-
ing thirty per cent smaller than
at present. The rising OF the
depressed land to the northward gave
the lakes their present dimensions, and
the oscillation then received check.
"A further fitting of the land to the ex-
tent OF three inches in each mile would
send great river from Chicago to the
Mississippi, reverse the current in the
Detroit, stop Niagara Falls and rob
the upper st. Lawrence of seven
eights OF its water" Whether, con-
trary to what appears to be law against
absolute stability, the oscillation has
entirely ceased or not, it is now so
slow as TO prevent the detection OF any
movement, the present level of the
water having remained nearly con-
slant for many centuries.
Other changes are, however, in
progress from the action of the rivers.
The St. Clair is feebly securing its
channel and building its delta; the Nj
agara is eating its way back to Lake
Erie; the st. Marie, Detroit and st.
Lawrence are deepening their chan
nels. "All these processes are too
slow to affect our hopes and fears con-
corning the immediate future, and for
our posterity in the year 10000 we
have no solicitude The men who
shall watch the draining OF Lake
Erie-or who, perchance, shall find it
worth their while to prevent twill
as far surpass us in powers and re-
sources as we surpass the men who
the lakes creation. For all
practical purposes our inland seas are
permanent, and their basins stable.
The only notifications that affect our
are those wrought by the
waves upon their coast" The changes
N the water levels that are noticed are
iue to the variations in the rainfall
Ipon the lakes themselves and upon
he land drained by the streams that
,our into them. The amount of rain
all varies from year to year and
rom one season to another in the
anne year, and the level OF the
water oscillates around an average !
position that remains fixed. Thus
Turing the period from 1860 to 1887,
he mean average range OF Lake
Irie was 1.6 feet, and the extreme
ange for the same period 3.5 feet. In
838 Lake Erie rose 18 inches above its
rdinary high stage, and in 1919 1t fell
! feet below its usual plane. "The
resent low water is the sequel OF last
drought" the lake region !
aviug received only about % inches Of !
ainfall instead Of its usual S3 inches,
his should cause fall OF the lakes of
bout IA inches. half from direct loss
nd half from the loss OF the streams
hat empty into them. But the average
all nf oil tho 1olrnu a,,lty = | u
lches, owing probably to the GOODNESS
the autumn, which retarded evapo- 7
alton. In Lake Superior the fall was ?
inches below the average low stage,
ie lowest point reached in seventeen p
ears, except on two occasions. In a
rie it was inches below the average. II
These variations relate to the entire u
irfaces Of the lake. A part of one II
ay be depressed and another part II
Used by gale especially in the y
lse Of Lake Erie, on account Of its =
A gale has been known a !,
raise the level Of one of its ends !.
wen on eight feet and to depress the II
her to an equal amount. Differences a
atmospheric pressures also effect =,
fferent parts Of the same lake, The u u
Ipid change Of air pressure, as In the "
$50 OF tornadoes, sometimes causes .,
lythmic undulations as high as the o.
rgest created by the wind. There are "
so tides which are as regular as on p
o ocean, but the highest spring tide II
ses only about three inches, while N N
Q average height is probnbly not u
ore than an inch.-C x. Gilbert in NJ
orum. VI