AND COAL-MEASURES OF I O W A. 



127 



are so densely interlaced, that it is penetrated only with great labour. The dark 

 shales in the lower part of Section No. 63, D, contain some imperfect seams of coal, 

 or rather, what might almost be termed mineral charcoal, since it presents the 

 woody, fibrous appearance of absolute, charcoal. 



After leaving the river bottom, the land rises in two beautiful terraces, the one 

 a hundred feet above the water-level, the other fifteen to twenty feet higher. The 

 first terrace is beautifully interspersed with groves, presenting delightful sites for 

 farms. The soil of both is exceedingly rich ; that of the first terrace is the 

 warmest, advancing vegetation with greater rapidity than the upland terrace. 

 The latter, however, is more durable, and contains so large a percentage of organic 

 matter, that when wet it is almost black. 



Below the Lizard Fork, at several places, shaly beds are exposed, including a 

 seam of coal four to six inches in thickness. At one point, the bed of coal lies 

 fifteen feet above the water-level, with a northerly dip, which brings it within ten 

 feet of the river in the distance of a few hundred yards. The tutenmergel struc- 

 ture is observable in some of these argillaceous beds ; and in the same vicinity are 

 black calcareous layers, like those observed above Brushy Creek. Low, broken 

 ledges of white calcareous rocks rise from beneath the shaly beds at the mouth of 

 the Lizard Fork, as seen on the right of the subjoined wood-cut. These beds are 



also seen at intervals for five or six miles. One hundred yards above the Lizard 

 Fork, on the main stream, the position of this limestone is well seen, where it forms 

 a distinct arch under the shale. 



Two miles above the Lizard Fork, this limestone forms a solid wall, twelve to 

 fifteen feet thick, the beds being much broken. 



At the Great Slide (Section No. 65), five or six miles above the Lizard Fork, in 

 latitude 42° 33', two imperfect seams of coal lie fifteen to twenty feet apart, above 

 and below beds of ferruginous sandstones, and underlaid by a great mass of shaly beds, 

 that by exposure crumble and give way, producing extensive depressions, and great 



