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POPULAR SCIENCE MONTHLY. 



Flaky particles of this size are easily carried along by a moderate 

 wind. In some places it appears as if the dust were resting on an 

 old land surface where no water could have been standing when it 

 fell. There is really no room for doubt that it was carried several 

 hundred miles by the wind. It must have darkened the sky at the 

 time, and it must have settled slowly and quietly over the wide plains, 



covering extensive tracts with a white, 

 snowlike mantle several feet in thick- 

 ness. What a desolate landscape after 

 such a shower! What a calamity for 

 the brute inhabitants of the land ! 



Right here in McPherson County 

 there was either a river or a lake at the 

 time of the catastrophe. This is plainly 

 indicated in several ways. In one place 

 the dust rests on sand and clay, with 

 imbedded shells of fresh-water clams. 

 It is assorted in coarse and fine layers 

 like a water sediment. Lowermost is a 

 seam of very coarse grains. These must 

 have settled promptly through the 

 water, while the finer material was de- 

 layed. In another place it lies on higher 

 ground, and here marks of sedges and 

 other vegetation are seen extending up 

 about a foot into the base of the deposit, 

 from an underlying mucky clay. Bog 

 manganese impregnates a thin layer just 

 above the clay, indicating a marshy con- 

 dition. Here also the material is some- 

 what sorted, but in a different way. It 

 is ripple-bedded. The water was evi- 

 dently shallow, if there was any water 

 at all. A burrow like that of a crawfish 

 extended down into the old clay bot- 

 tom. On a slab of the volcanic ash 

 itself some tracks appeared (Fig. 4). 

 These were probably made by an indi- 

 vidual of the same race in an effort to escape from the awful fate of 

 being buried alive like the inhabitants of Herculaneum and Pompeii. 

 The shower must have lasted for a time of two or three days. I 

 infer this from the nature of the wind changes, which are indicated 

 by the ripples in the dust. These still lie in perfect preservation (Fig. 

 5), and may be studied by removing, inch by inch, the successive 



Fig. 4. — Tracks in the Volcanic 

 Dust, probably made by a 

 Crawfish. Reduced to % di- 

 ameter. 



