Identifier: transactionsmining27amer (find matches)
Title: Transactions
Year: 1871 (1870s)
Authors: American Institute of Mining, Metallurgical, and Petroleum Engineers
Subjects: Mineral industries
Publisher: New York (etc.)
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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s evidently destroyed by acyclone, and the trees were blown into the lake. As the lakefilled up, these trees were buried, and many of them have beenfound in excavating for foundations and sewers. Trees foundin 1871 show magnificent growth—the annual rings indicatingat least 250 years age. Most of these trees have been found without branches,stumps or roots, and showing the effects of the cyclone. Theexact date of the destruction of this forest can be only approxi-mated. It is supposed, however, that the formation of thesand-bar upon which this timber rests began with the firstnorth wind after the disappearance of the glacial ice at thesouth end of the lake.—the same wind that built 5 miles ofsandy plains in the Calumet region,—and the conclusion ispretty well supported that the time occupied in forming thissand-bar represents the first epoch after the close of the glacial THE CHICAGO MAIN DRAINAGE CHANNEL. 293 period, and the one during which grew the forest of which the Fig. 3.
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AyEKICAN BANK NOTE CO., N.Y. Drains at Site of Chicago, Transforming the Bay of Fig. 2 into an Inland Lake. buried timber was a part. The destruction of this forest and 294 THE CHICAGO MAIN DRAINAGE CHANNEL. its burial mark the close of the first post-glacial epoch and thebeginning of the second. This takes in the tilling of the inlandlake with wind-drifted sand from Lake Michigan and silt oryellow sandy loam from the turbid floods of the North Branchand the Des Plaines. If this conclusion is correct, the age otthis timber is approximately 6000-years; for in 8000 years notonly has a considerable part of the site of Chicago been depos-ited by the process above described, but 5 miles of the southend of Lake Michigan have been filled up. Fio-. 4 shows the site of Chicago as it looked in 1812, showingold Fort Dearborn, Indian encampments, and the battle-groundof 1812 Down at the southwest corner, what is known asLees place marks the site of Marquettes winter quarters in1674-75 when he wit

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