Arncricaii Association Meeting. 259 
Taylor's Falls. Minn., so late as the Buchanan interglacial epoch, pre- 
ceding the Illinoian and lowan glacial readvance; and the channel of 
the Mississippi from Minneapolis to Fort Snelling, eroded during the 
Postglacial period, has afiforded to Prof. N. H. Winchell his well 
known estimate of that period as between 7,000 and io,oco years. 
11. Supposed "Corduroy Road" of Late Glacial Age, at Amboy, 
Ohio. By Prof. G. Frederick Wright, Oberlin, Ohio. This 
paper detailed the discovery of a series of logs lying side by side as 
in a corduroy road, and extending for a distance of 200 feet or more, 
which were covered by 30 feet of gravel in which were found the tooth 
and tusk of a mammoth, the tusk being ten feet long, twenty-two 
inches in circumference at the base, and weighing 155 pounds. The 
resemblance to a corduroy road was indeed very striking; but the 
appearance of the logs showed that they were driftwood, and had been 
buried by the accumulation of the gravel that took place along the 
old shore of lake Erie, when, during the closing centuries of the 
Glacial period, the water was held up to a level 150 feet higher than 
now. The logs and base of the deposit are 140 feet above the lake, 
and about four miles back from it, on the banks of Conneaut creek, in 
the extreme northeastern corner of Ohio. The gravel was evidently 
brought down from the higher lands to the south, near the sources of 
the creek, and was deposited with the mammoth remains in a delta 
at the edge of this old glacial lake. In connection with this in- 
vestigation, it was ascertained that similar deltas of gravel characterize 
the margin of the old lake where other streams from the south met 
it at various places between this point and Cleveland. Altogether 
these observations give a very vivid picture of the rapidity with which 
coniferous forests proceeded to cover northern Ohio as the ice melted 
back, and of the promptness with which the immense animals of the 
time reoccupied the territory. Important inferences are also derived, 
showing that the period of time during which the water remained at 
the high levels of the old ice-dammed lakes was short. 
12. Changes in the Drainage System in the Vicinity of Lake On- 
tario during the Glacial Period. By Dr. M. A. Veeder, Lyons, 
N. Y. The paper noted sections of wells in buried river channels 
south of lake Ontario, from the Niagara river eastward to the Mo- 
hawk valley. 
13. Recent Severe Seismic Movements in Nicaragua. By John 
Crawford, Managua, Nicaragua. Description of a series of earth- 
quakes in western Nicaragua, April 29th to May 12th of this year, as 
reported by the author in this magazine for July (vol. xxii, pp. 56-58.). 
14. Another Episode in the History of Niagara River. By J. W. 
Spencer, Washington, D. C. This paper is a sequel to one read 
before the American Association four years ago on the duration of 
Niagara falls. It announces the discovery that while the falls were 
receding from Foster's fiats to the locality of the railway bridges, the 
fall of the river reached its maximum amount of 4^:0 feet by the 
