p.2

[illustration of strata]

That these Azoic rocks are of great age is fully shown by numerous sections where they are overlaid non-comformably as represented in the figure above, by the Potsdam Sandstone, which, if we except the Eozoon belongs to the oldest period in which organic remains are found. It will be seen that the old rocks had been deposited, had become consolidated, had been tilted, and then upturned edges eroded, before the deposition of this oldest of life-bearing sandstone; These junctions are well exhibited on the Menomonee river (of Green Bay); at Swallow Bluff near Grand Rapids on the Wisconsin; and at a point a little below the Black river falls.

-thus showing a great lapse of time between the epochs of the formation of these two series of rocks.
It was here that this important fact was first recognized by Col. W. Foster and made known in his report in 1851.

Foster & Whitney, Rep. Geol. L. Superior part 2 p 8, 1851