For a succession of geologic ages our county, in common with eastern Iowa, seems to have remained dry land, for no deposits of the sea are found upon it. On both sides of the continent mountain ranges of Alpine height were uplifted, and during the immeasurable years worn down, grain by grain, to flat and featureless plains. But no deformations are recorded in our county history and the lands seems to have remained so low that little erosion was possible. We are permitted to conceive that over our savannas in Mesozoic times there roamed monstrous reptiles of strange shapes, such as are known to have existed in adjacent states. In the later ages of this era it is not impossible that during the great submergence which brought the Cretaceous sea over the Great Plains from the Arctic to the Gulf, including western Iowa, our area also may have been inundated and huge swimming reptiles such as are found in the deposits of Kansas and Nebraska may have disported themselves where now our rich farm lands lie open to the sun, while in the air featherless cold-blooded creatures larger than any bird winged their way on leathery pinions. [Illustration: THE ASTOR HOUSE Erected by John Young in 1839, Looking South The Second House in Cedar Rapids COURTESY CARROLL'S HISTORY] During the millions of years which are included in the Tertiary ages Linn county was undoubtedly dry land. On our grass lands pastured a succession of strange and uncouth mammals evolving into higher and higher forms. Among these denizens of the county were probably herds of pig-like creatures, three toed horses little bigger than foxes, and ancestral monkeys swarming in the trees, for such are known to have existed in other states. But these chapters in the history of the county can not be written from any local records. THE GLACIAL EPOCH The warm climate of Tertiary times changed slowly to one of arctic cold. The winters lengthened and the summers becoming ever cooler and yet cooler failed at last to melt the winter snows. Vast sheets of glacial ice, such as that which shrouds Greenland today, covered much of the continent. The geologic panorama thus presents our area as buried beneath one after another of slow-moving glaciers hundreds of feet thick. The proofs of their existence are found in almost every cutting which goes below the soil. Any quarry will show the rock deeply rotted and pitted by long preglacial decay. Here and there upon its surface will be found remnants of the deep red residual clays, the subsoils of preglacial times. Upon these clays formed from the decaying rock rest stony clays in which clay, sand, and stones faceted as only glacier ice can facet, are mingled pell-mell together, as only glacier ice can mingle. Occasionally is found the unmistakable track of the glacier left on the underlying rock scraped smooth and marked with parallel scorings, as at the north end of the cut of the Chicago, Milwaukee & St. Paul Railway at Linn Junction.