Wherever found the Independence contains nodules of silica, which may reach a foot in diameter, and often angular fragments of the same material which may be as fine as sand. The formation is marked by irregularities of deposition, channel cutting by drift currents, lenses of calcerous material, and rapid lateral change in the form and constituents of the rock. All of these characteristics point to the deposition of this formation in a shallow sea near shore. Indeed, some of the beds were apparently laid in marshes such as are now found along low ocean shores. Thin seams of coal formed in the Independence were once peaty deposits preserved by the presence of water from the decay which returns dead vegetable matter to the air. In 1871 such a seam of coal, not exceeding an inch in thickness, was found at a depth of ninety feet in a well on the farm of Mrs. C. Hemphill, near LaFayette. Pieces of the coal were taken to Cedar Rapids and Marion. A mining company was formed, and without seeking for any expert advice from geologist or mining engineer, and without any tests of the extent and thickness of the seam, a shaft was sunk after the precious fuel. Water was encountered in such quantities that expensive pumping machinery was used, and in all several thousand dollars were wasted in a search which any competent geologist could have told was foredoomed to failure. THE DAVENPORT LIMESTONES The sea over eastern Iowa deepened after the deposition of the Independence, for there was now deposited upon its floor limestones in place of shales. The lowest of these, known as the _lower Davenport_ beds, are hard, compact, and of finest grain, and so far as known are unfossiliferous. The _upper Davenport_ is a tough, gray, semi-crystalline limestone which contains an assemblage of fossils of many species. Highest of these are the first vertebrates to appear in Iowa so far as our records go. Fishes which swam over our area left to be imbedded in the limestones their hard enameled teeth and fin spines. The most common of the Devonian fishes was a small shark. In several other counties the lower and the upper Davenport limestones retain the attitude of their deposition. But everywhere in Linn county they have been broken into bits and re-cemented, forming breccia. These brittle rocks could hardly give way to such immense stresses without causing sharp and violent vibrations to run through the crust of the earth, and we may therefore list great earthquakes as a part of the history of our area in Devonian times.