Allen.] 248 [January 21. 



tion of coal in our grates, and varying from a few inches to two feet 

 or more in thickness. Below this layer there is only a slight discolor- 

 ation and hardening of the subjacent clay. Above the bed of cin- 

 ders occurs a bed of indurated clay, of a bright brick red color, vary- 

 ing in thickness from a few feet to twenty or more ; still above this 

 are generally several feet of indurated reddened sandstone. The 

 whole thickness of the strata showing more or less strongly the effect 

 of heat, may amount to thirty or even fifty feet, but the more common 

 thickness rarely exceeds eight to twelve. Generally but a single 

 reddened band is seen at a given point, which may extend for many 

 miles, capping all the ridges and isolated buttes as far as the eye can 

 reach, which hence all rise to a uniform level. Occasionally the 

 metamorphosed beds occur at a relatively lower level, with a consid- 

 erable thickness * of unmodified clays and sands above the reddened 

 beds. Again, as in the Bad Lands of the Little Missouri, and in 

 other regions where the surface is deeply scored by erosion, several 

 of these reddened bands are exposed, situated one above the other, 

 separated by fifty to one hundred or one hundred and fifty feet of 

 soft clays, marls and sands, they preserving their relative positions 

 and almost perfect horizontality for many miles. Generally the. 

 metamorphism is limited to the hardening and change of color of the 

 superjacent clays and sands, but where the burned out lignite beds 

 were several feet in thickness, the strata immediately in contact with 

 the lignite have been more or less fused or at least reduced to a 

 more or less plastic condition. This is evident from the vitreous, 

 porcellanic and vesicular structure of the different portions of these 

 lower beds. 



At points where this igneous action has been most intense, we find 

 almost every variety of scoriaceous material, undistinguishable in ap- 

 pearance from true volcanic lavas and pumiceous matter. As already 

 mentioned, the lowermost of the metamorphic series of beds consists 

 of cinders and clinkers, not much unlike the residuum left in our coal 

 grates from the combustion of ordinary coal. It is generally of a 

 whitish or grayish color, portions of which are so soft as to be easily 

 crumbled in the hand, or crushed under the foot ; but the greater 

 part is made up of hard, rough, vesicular masses, with the larger inter- 

 stices filled in with ashy or earthy matter. The material next above 

 this layer of cinders shows signs of having been in a plastic or semi- 

 molten condition. It presents a great variety of colors, from white, 

 through yellowish white, olive and yellow, to dark brown, purple, and 



