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Show 221 bnttonwood, seven of sassafras, five of magnolia, one fig, one palm, and two of cinnamon. The last four were probably hardy species of their kinds. Still they indicate a warmer climate than now exists. When we ie3ollect that at the period of their growth, this part of the coantry was nearly on a level with the ocean, and the dry land was comprised principally of a few islands, the variance of the climate is easily explained. These are " the first known of the great modern group of Angiosperms," " and the ordinary fruit- trees of the temperate zones," for leaves of the Pyrus and Prunus, allied to the pear and plum, have also been found. The contrast between this fossil flora and the plants of the older formations is very strong, while its resemblance to those now living is equally remarkable. The interest attached to this numerous variety of modern plants is enhanced by the fact that in the earlier formations no dicotyledons are found, the conifers which come down from the Devonian age being the highest type. But in our Dakota and the corresponding age in Europe we have a sudden influx of new types covering Dearly all the forms now living. The large proportion of orders and genera to species is very remakable. The numerous indications show that the trees must have grown on islands near the shore- line, and that the leaves were imbedded in the marine sediment immediately after dropping. Worm- borings are also found in the same strata with the leaves. A few fish and one saurian ( Hyposaurus vebbii) have been foand in this group. ID the Dakota group, there are a few veins of brown lignite, which is always an inferior variety of coal. The most important seam extends irregularly, and with frequent omissions, from the State line in Washington and Republic Counties, southwesterly to the Arkansas Valley. It varies in thickness from 10 inches to 40; but usually a portion of this thickness includes seams or layers of clay- shale. This lignite contains a large percentage of ashes; but a more objectionable feature is its tendency to crumble on exposure to frost. This alone renders it almost worthless as a marketable coal. At some localities it has much pyrites, with sulphur so free as to cover the deposit with a yellow eoating. This coal sometimes takes fire by spontaneous combustion. Notwithstanding these defects, it becomes of value in sparsely- timbered counties, by furnishing to the settlers a cheap fuel, costing only the time and labor necessary to dig and convey it to their farms. It is usually mined at the surface in the open air, by " stripping,* i. e. removing the few feet of soil or shale that overlies it. An average outcrop till yield at least a ton for a day's labor. It is found in Washington, Republic, Cloud, Mitchell, Lincoln, Ottawa, Saline, Ellsworth, McPher- * OD, Bice, Barton, and perhaps some adjoining counties. The average * idth of the Dakota is less than fifty miles, being somewhat less than Jiat in the north part of the State, and more on the Smoky and Arkansas Rivera. The dip is to northwest and very slight. It is difficult to lecide the amount, but it does not appear to be on the average more tan 5 feet to the mile. It is conformable to the Fort Hays lime forma-ioQ above it. It corresponds very nearly to the Cretaceous of Swal-ow's Report, p. 9, and also to Kos. 2 and 3 of his Triassic.* The naximam thickness of this group may be 500 feet. It is difficult to stimate the thickess, as the larger portion of the material consists of sand-stone, much of which was originally thrown down in oblique deposits. The total thickness of the Cretaceous in Kansas we estimate to be Wfeet. < • The other numbers of his Triassic belong to the Perniio- Carboniferons. |
