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L, Lesquereux on the Coal Formations of North America. 29 
by the outward direction of the wall of a basin an upper bed 
ought to be extended somewhat beyond the lower and cover its 
margin. It is the case in the western borders of the Kentucky 
coal-fields, viz. in Christian county and other places, where the 
4th coal above the conglomerate or the next bed below it, abuts 
against the older formation, when the lowest coal has to be 
looked for farther back towards the centre of the basin. On both 
the opposite sides of the Appalachian and the Illinois coual-fields, 
the appearances are different. It is the lowest coal, then the 
conglomerate, then the sub-carboniferous strata that appear one 
after the other upon the surface, following a dip corresponding 
to that of the sides. This undoubtedly shows that they a 
pated in the movement which elevated the ridge that divides 
them, and that they were formed before its upheaval. 
he undulations of the surface of the coal-fields, so dis- 
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5. The upheaval of the Alleghany mountains and the undu- 
lating movement caused by it upon an immense surface of 
country was very slow, and continued for a long period. The 
bends or flexures of the eastern coal, especially of the anthracite 
coal-fields are not jagged and angular, nor are they often broken 
raised sides, as if the matter had slipped by its owm weight when 
there was room for a displacement. nN it follows that if the 
undulating movement was slow, and if the strata of the eoal 
measures were still in a soft state and easily removable, the top 
of the great ridge was necessarily and easily washed away as 
fast as it was being raised near and above the surface of the sea. 
No wonder therefore that the remains of the coal strata have not 
mn preserved, and that we scarcely find any trace of them. 
The total sek of the coal washed away by erosion, is, 
I think, the only objection of any —— t that has been or may 
be mad i ad i 
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