Evening star. [volume] (Washington, D.C.) 1854-1972, 1889-04-12
CITY AND DISTRICT.
THE AGE OF NIAGARA.
Prof. Gilbert Thinks That Il Is Com
paratively New Thing.


THE RATE OF RECESSION SHOWS THE FALL TO
BE ABOUT EIGHT THOUSAND YEARS oID-wHEN
The GEOLOGICAL PLANE TILTs BACK THE
GREAT LAKES MAY EMPTY INTO THE MISSISSIPPI
AND NIAGARA MAY DISAPPEAR.
Prof. Gilbert. of the L. S. geological survey,
entertained large audience in the lecture
room of the national museum yesterday after
noon by reading his paper on the subject of
the history Of Niagara Falls His lecture was
the last in the first half of the course of what is
popularity known here as Saturday scientific
lecture" but he deferred to the snow storm of
Saturday, and gave the paper yesterday instead.
Behind. on the great white screen, was
number of maps and charts illustrating points
in the lecture. At Ais Major Powell, director
of the geological survey. introduced Professor
Gilbert, referring to the Niagara Falls as one
of the natural wonders of this continent to-
gether with the Mammoth cave the grand canon
of the Colorado, Yellowstone park and Crater
lake.
The great cataract. said Prof. Gilbert is the
embodiment of power. forcing one TO the reai-
cation of the insiCnfcance of humanity. of the
puny stature and force of man. 1t Is also an
obdUrate geologic fact. problem with which
scientists have been graphing for years. and
from which but comparatively small results
have been obtained.
THE GEOLOGIC FEATURES
Then the professor plunged into a discussion
of the geological features of the case as deep
the basin of the falls itself The country
underlying Lakes Erie and Ontario he ex-
planned, have the characteristics of the car
bOniferous, Devonian and Silurian formations
Lake Erie is eXcayated by the great body of
DeyOnian shale lying between the other two. and
Lake Ontario from the Silurian rock. The car
boniferous elements peep up some distance to
the south OF the lakes. Between Lakes Erie
and Ontario run two projecting. outcrOpping
ridges. the most nOrthward of which. a steep
cliff, being called the Niagara escarpment over
which the Niagara river originally tumbled.
The fall of the water from lake to lake il 2q6
feet. one-hdlf of which is accomplished at a
single leap. at what Is world renowned as the
great falls of Niagara. From Lake Erie to this
point the river l. broad and shallow. the bed
being cut through the shdle of the DevOnian
age. From the falls to Lewiston the river runs
between hard limestone cliffs. in a narrow chan
mel. and from Lewiston 10 Lake Ontario the
stream Is broad and deep. having cut its way
through the softer Silurian shale The work
OF the river in thus forcing its way through the
rocks Is called erosion.
THE GREAT LAKES,
Prof. Gilbert said. looked for their origin to
the ice age. when glaciers covered the northern
portion of the United States and ground out
hollows which afterward formed the basins for
the lakes. He explained that the object of his
paper was 10 Set at some idea of the age of
Niagara. a task which has always baffled geolo-
glsts. and he pointed out the fact that the
chronology of the geOlOgst and that of the his
tOrian are difficult to adjust. There have been
a number of estimates as to the age of the falls
he said. which have all had one and the same
method of ascertaInment. namely, calculation
upon the basis of the distance between the falls
and the escarpment and the present rate of the
recession OF the falls. together with certain
surrounding qualifying conditions. The diff
Guilty lies FIRST III the lack of accurate knowledge
OF the rate OF recession. 1t has been estimated
with great variety of results. from three feet
In one year to one foot in century Indeed
one geOloglst has gone so far as to claim that
the falls do not recede at all. but are. have
been. and will be stationary. In 1912 Prof
John Hall. whose name and reputation are a
by-wOrd with Younger biologists made a care
full survey of the falls and placed points so that
future observations could be made In 1875
another survey was made. and still another
under the auspices of the geological survey in
1856 The record of these three surveys COW
ering period of forty-four years. furnishes a
clue TO the rate at which the falls have been
moving southwark.
THE ANNUAL RATE OF RECESSION
The estimate, based on these facts. is that for
the past fOrty-fOur years the falls have receded
at the rate of 2 40 feet in year. The Horse
shoe falls are at the head of the gorge. and the
American falls at the eastern side, but the time
was when 10th were together, before the little
point called Goat Island was reached The
recession Is more rapid at the center than ON
the sides; as the crest of the Horseshoe falls
retreats the water tends to concentrate there
and the time VIII probably come when the
sides OF the present falls will have become dry
shores. The gorge is known TO be $500 feet
long. A calculation has shown that on this
basis the falls began to wear away the rock of
The escarpment near Iewiston-which had not
then taken out city charter-abOut 800 wears
ago. plus or minus certain items which NAV
affect the rate of recession.
Ihe limestone Is not worn; il is not ground
of by rocks or debris in the water which comes
TO the Falls from the clear depths of Lake
Erie The process Is brought about by the
undermining of the shale. which seems to dis
lntegrate and suddenly crumble. Frequently
great masses break loose and fall over the
brink. thus changing the character of the fall
deep basin of an unknown depth has been
secured out at the foot. probably by means of
ice, which comes over the Falls in great guam
Titles IN the winter.
UNCERTAIN FACTORS
The lecturer dwelt at length on the dificul-
ties presented by the varying factors whose
influence Is by no means certain. The rate Of
recession probably depends upon the height
OF the Falls, which has not been ALWAYS the
same, or upon the amount of floating ice, upon
the changes IN the volume of water the
amount of evaporation from Lake Erie the
local rainfall. and number of other condi-
lions These go TO make the problem of dis
covering the age of Niagara difficult if not
impossible Of solution
Prof Gilbert took the audience through a
geologic tour away back in the ice age and
showed how the Great Lakes were formed. The
passing away OF the glaciers. their disappearance
toward the north has been accompanied by an
upheaval of the land. gradual di5 of the gen
eral plane toward the southwest which caused
the great lakes 10 take their present course.
Lake Huron once had its outlet by way of the
north emu, out the ultng process spilled the
water southwark and it found an outlet thronyh
Lake Erie and the Niagara river. There is
some reason to believe that this change in the
plane OF the surface Is complete but If il is not
and continues, the outlet of the lakes will be
from point near Chicago to the Mississipni
the currents OF Lakes Erie ST. Clair. and Hu-
ron will be reversed. and Niagara river and the
falls will be wiped out of existence
lrnI-ISES