TO JUNCTION OF GRAND AND GREEN RIVERS. 17 



remarked by Professor Hall in the structure of the coal-basins, going from north to 

 south, and by myself from northeast to southwest, is not uniformly progressive through- 

 out their entire extent, but was modified locally by the sinuosities of the shore-line of 

 the northern main-land, and by the presence of islands at a greater or less distance from 

 the shore toward the south and southwest; in illustration of which we may cite the 

 comparative barrenness uf the Coal- Measures of Northern and Central Illinois, where, 

 as in Kansas, the calcareous strata, vastly predominate, with the greater development 

 of strata and mechanical sediments in Southern Illinois and Kentucky; so also the 

 productive Coal-Measures of the region about Fort Belknap, in Texas, where the quan- 

 tity of carbonaceous and sandv matter is equal to, if not greater than, that of Kansas 

 directly north. At Saute Fe, also, as will be seen from the description hereafter to be 

 given of the geology of that vicinity, the Carboniferous series includes a great thickness 

 of coarse sandstone filled with the impressions of land-plants, evidently transported no 

 very great distance from their place of origin. As we progress southward, however, 

 we ultimately reach the limit of traces of the existence of terrestrial surfaces during 

 the coal period, as in Southern and Southwestern New Mexico, where the entire Car- 

 boniferous series is represented by a calcareous mass, all an organic or chemical pre- 

 cipitate from the waters of the ocean, and the proof of the uninterrupted existence of 

 an open sea in that region throughout the entire carboniferous epoch. 



Coal. The coals of Missouri and Kansas have all, to a certain extent, a common 

 character, as compared with those of the Alleghany coal-fields ; they are softer, and 

 contain a larger amount of volatile matter, of water, and of sulphur. Some of them 

 are cannel, frequently handsome and of good quality, and those which are not strictly 

 cannel are more or loss like it in chemical composition and physical structure, and they 

 frequently have layers of cannel running through them. They are generally quite 

 tender, and when exposed to the action of the weather, like the Cretaceous and Ter- 

 tiary coals of the western part of the continent, which they so much resemble, they 

 are prone to "slack," or to break up into innumerable rhomboidal or cubical fragments. 



The causes of the peculiar character of the coals of Kansas are to be sought, I 

 think, in the physical conditions attending their formation, rather than in any peculi- 

 arity of the vegetation from which they were derived. In a paper, published in the 

 American Journal of Science, of March, 1857, I have attempted to show that the char- 

 acters which distinguish cannels from other bituminous coals are for the most part due 

 to the excess of water in which they were submerged during the process of their for- 

 mation. I have also been led to suppose that this cause has, to a considerable degree, 

 given to the western coals the characters they exhibit; that the carbonaceous matter 

 composing them was, during its accumulation, more thoroughly saturated or more 

 completely submerged than that composing the coal-strata of the Alleghany basin; 

 and that when the coal-seams had attained their entire thickness they were not imme- 

 diately buried beneath heavy masses of mechanical sediment, by the weight of which 

 all the effects of great pressure would bo obtained, but, instead, were submerged per- 

 haps deeply beneath water, the pressure of which would be expended in all directions, 

 and would, therefore, not -act as a distinct compress on the saturated mass. That the 

 chemical characters of these coals have been in any great degree modified by this cause 



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