The Grenada gazette. (Grenada, Miss.) 1885-18??, 1888-08-02
THE GREAT LAKES.
sociological History of Their Formation and
Change In Their Level.

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-
ton 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 the
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 it 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-thrd as long as now, and
its surface was only one-tifth as great.
Toledo, Cleveland and the Bass Islands
being far inland. When Lake Ontario
forced a 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 a great river from Chicago to the
Mississippi, reverse the current in the
Detroit. stop Niagara Falls and rob
the upper St. Lawrence OF scy~n-
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 feehIy securing its
ohnnna1 ""d 1'..il@;- r i,s 1alta. tho 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-
cerning 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
watched the lakes creation. For all
practical purposes our inland seas are
permanent, and their basins stable.
The only notifications that affect our
economy are those wrought by the
waves upon their coast The changes
in the water levels that are noticed are
due to the variations in the rainfall
upon the lakes themselves and upon
the land drained by the streams that
pour into them. The amount of rain
fall varies from year to year and
from one season to another i'll the
same year, and the level OF the
water oscillates around an average
position that remains fixed. Thus
during the period from 1860 to 1887,
the mean average range OF Lake
Erie was l.6 feet, and the extreme
range for the same period 3.5 feet. In
1888 Lake Erie rose Is inches above its
ordinary high stage. and in 1919 it fell
81 feet below its usual plane. The
present low water is the sequel OF last
summers drought" the lake region
having received only about 25 inches OF
rainfall instead of its usual 33 inches.
This should cause fall of the lakes Of
about IA inches, half from direct loss
and half from the loss OF the streams
that empty into them. But the average
fall of all the lakes was only about Z
inches. owing probably to the GOODNESS
OF the autumn, which retarded evapo-
ration. In Lake Superior the fall was
inches below the average low stage,
the lowest point reached in seventeen
years, except on two occasions. In
Erie it was 2 inches below the average.
These variations relate to the entire
surfaces of the lake. A part of one
may be depressed and another part
raised by a gale especially in the
case of Lake Erie on account of its
shallowness. A gale has been known
to raise the level of one OF its ends
seven or eight feet and to depress the
other to an equal amount Differences
in atmospheric pressures also effect
different parts of the same lake. The
rapid change Of air pressure, as in the
case of tornadoes, sometimes causes
rhythmic undulations as high as the
largest created by the wind. There are
also tides which are as regular as on
the ocean, but the highest spring tide
rises only about three inches, while
the average height is probnbly not