It is really difficult to appreciate the change such a shower must have produced in the appearance of the landscape, and the effect it must have had on animal and plant life. So far away from the volcanic source, the wind can not have laid down a layer of this dust several feet in thickness without scattering it far and wide all around. It must have covered tens of thousands of square miles. Just imagine, if you can, a whole State, clad in the verdure of summer, suddenly, in two or three days, covered over by a blanket of white volcanic ash! Many species of plants must have found it impossible to grow in such a soil. And what disaster it must have caused in the animal world! Grazing herds had their sustenance buried from their sight, and could save their lives only by traveling long distances in this loose dust. Many a creature must have had its lungs or its gills clogged with the glassy flakes floating in the water and in the air. The sudden disappearance of several mammal species near the beginning of the Quaternary age has been noted by paleontologists. Does it seem unlikely that an event like this, especially if repeated, may have hastened the extermination of some species of land animals? That many individuals must have perished there can be no doubt. Not very far away from that outcrop of the dust which I have described, one of the early settlers in this part of the State once made a deep well that penetrated the ash. Above the deposit, and some sixty feet below the surface of the prairie, he found what he described as "an old bone yard." In digging other wells in this vicinity mammal bones have been taken up by the settlers from about the same horizon. It is to be regretted that, with one exception, none of these fossils have been preserved for study, for it is likely that they were the remains of animals which were killed in the dust shower. In the absence of fossils definitely known to be connected with the ash, its exact age seems yet uncertain. In McPherson County it is underlaid by clay, gravel, and sand, which contain remains of the horse, of a megalonyx, and of bivalve mollusks of modern aspect. In the bluffs of the Missouri River near Omaha pockets of a similar ash rest on glacial clay under the loess. At the latter place it must belong to the Pleistocene age, and at the former it can not be older than the late Pleiocene. These two deposits may not belong to the same shower, but it appears, at any rate, that the volcanic disturbances which produced them occurred near the beginning of the Pleistocene age.