470 ORIGIN OF THE APPALACHIAN COAL STRATA, 



rect, then have wc, in every stratum of the series, not merely a 

 new picture of the physical gcogi'aphy of the region, but a clear 

 legible record of the very changes, gradual or tempestuous, of 

 w^hich each in its turn was the result. We unclasp, as it were, a 

 whole volume of hydrographic charts, displaying, for a vast suc- 

 cession of epochs, the ever-changing relations of the land and 

 waters. A wdde tract of ancient coast is at one time occupied 

 by the ocean, at another by an immense plain, filled with green 

 marshes and swamps, and at another by dry land, clothed with 

 an impenetrable forest. But we behold more than merely these 

 several conditions of the surface ; we perceive the very transitions 

 themselves which revolutionized the geography ; we discern the 

 ocean in the very act of encroaching on the land, forming exten- 

 sive marshes, where before the whole was solid shore ; we actually 

 trace it in its gradual retreat, exposing its own marine sediments 

 to form a fertile soil for vast savannahs of the Stigmarice, and 

 again we see the entire region embracing the dryland, the marshes, 

 and the sea, heaving and undulating in the biUows of the irresist- 

 ible eai'th quake, the ocean and the land contending for mastery 

 in the tremendous conflict. 



If the Appalachian coal strata, whose history I have here en- 

 deavoured to interpret, exhibit truly the above-imagined conditions 

 and events, we may consider the entire formation as constituting 

 a stupendous tide-gage, registering the lengthened ebbings and 

 flo-wings of that ancient sea, and the stormy agitations of its 

 eternally oscillating waters, as the epoch of its last, greatest move- 

 ment, and final drainage, drew near. 



Of the Gradation in the Proportion of Volatile Matter 

 IN THE Coal of the Appalachian Basins. 



There prevails a very interesting law of gradation, in the quan- 

 tity of volatile matter belonging to the coal, as we cross the Ap- 

 palachian basins from the southeast towards the northwest. The 

 extraordinary extent of area over which this law obtains, and its 

 intimate connection with con-esponding gradations in the struc- 

 tural phenomena of the region, the description and theory of 



