122 Tlie American Geologist. February, laus 
eating- the changes in the near future. From the northeast- 
ward tilting of the lake region, it was computed that in 5,000 
years, not merely Niagara falls would cease to exist, but also 
that the drainage of the deepest part of the Niagara river at 
Bufifalo (45 feetj would be reversed and turned into lake 
Erie, whose outlet would then be through lakes Huron and 
Michigan into the Mississippi river by way of Chicago, lliis 
inference was based upon the long delayed discovery of the 
rate at which the earth's crust has been rising in the lake 
region, — wdiich was found to be for the Niagara district 1.25 
feet per century more than the rate of rise at Chicago.* With 
this determination it was easy to calculate the rate of terres- 
trial deformation for other regions,— thus northeast of lake 
Huron the rise has been found to be two feet per century, and 
north of the Adirondack's, the warping is progressing at 3.75 
feet in a hundred years. 
The rate of deformation of 1.25 feet per century, in the 
Niagara district, was the minimum calculation, with a possible 
maximum of about 1.5 feet per century. The approximate 
correctness of the determination has just been confirmed by 
a paper presented to the American Association, by Prof. G. K. 
Gilbert, immediately before this communication was read.t 
He had used the bench-marks at various localities where the 
fluctuations of the lake levels have been registered the last 20- 
37 years. While the recorded measurements vary from about 
one to two and a half inches during the periods of observa- 
tion, they have been extended over the lake region, with re- 
sults closely agreeing with the previous determinations of the 
writer. This will be l^etter imderstood using Prof. Gilbert's 
application — namely, — that in 500-600 years, the Erie waters 
would be on a level with those of lake Huron- — in 1,000 years 
they would overflow the natural divide near Chicago — in 2,500 
years, the waters would cascade into the Niagara gorge only 
during high water — and in 3,000 years, the falls would be en- 
tirely drained. These changing conditions, based upon the 
writer'.s previously discovered rate of terrestrial deformation, 
would take — 720 years for the Erie and Huron waters to be 
*See Duration of Niagara Falls, cited before. 
t Modification of the Great Lakes by earth movements. Nat. Geog. 
Mag., vol. VIII, 1897, pp. 233-247. 
