PROF. HARRIS. NOTES OX OUR LOCAI, GEOLOGY NO. II. IfiT 



power that could have wrought a denudation so vast as to sweep 

 away the superincumbent mass of shales, limestones and solid rock, 

 is beyond our conception; and yet it is this power that makes the fu- 

 ture Mississippi River a possibility. 



Supposing now that before the time of the Coal Measures, a denu- 

 dation of such magnitude has swept away (just as we see it now) all 

 trace of the Hamilton, except in the cliff between Rock Island and 

 Moline; all trace of the still lower fossiliferous rock; extending down 

 still deeper, until, in the non-fossiliferous rock, it lias unroofed one 

 of the ancient subterranean water-courses in which it abounds. Ev- 

 erything is now ready for the waters of the Coal Measures; and the 

 same sea that fills the cavity in the Hamilton in the quarry between 

 Rock Island and Moline, is brought into direct contact with this old 

 water-coux-se, thus furnishing the material with wliich it was filled. * 



1 have already, in a preceding i)age, spoken of the layers that com- 

 posed the clay in which the fucoid was imbedded, that there was ev- 

 ery evidence of their having been deposited gradually and in quiet 

 waters. That this plant could have floated from some other i)osition 

 and simply been swept into the locality where we now found it, 

 seems scarcely possible when we consider the peculiar condition and 

 quiet repose in which it is found. The portions now in our posses- 

 sion give us but an inadequate idea of the beauty and delicacy of 

 structure characterizing the extremities of the plant. The sandstone 

 had gradually thinned out until it graduated int(j the soft blue clay; 

 and for several inches upon this blue clay, could be traced the finer, 

 more attenuated and delicate impressions of its branchlets, but the 

 clay was so fragile, it was utterly impossible to preserve them. 



There was no confusion; no folding of part on part; no botanist in 

 his herbarium ever arranged his treasures with more exquisite taste 



* Note. Since writing the above, 1 have been iufornied by >Ir. Pratt, of 

 the existence of several ismall patelies of rocks of the Coal Measures, over 

 the area referred to. They exist, not in the form of soft shale, but of hard, 

 dark grej', iron-stained sandstone, tilled to repletion with fragments of (!oal 

 plants. One of these, at the government bridge, exposed in excavating for 

 the draw pier, and on which the pier rests, is especially note-worthy as ap- 

 parently belonging to a bed of some extent. The river bed at Moline also 

 exhibits the same rock. 



The existence of these i)atches in so many phices, resting in all cases up- 

 on the partially denuded portions of the non-fossiliferous rocks, can only be 

 accounted for on the complex theory of-tirst ; the total disai)pearance of the 

 Hamilton shales and limestones, and-secoudly ; after such erosion, the inun- 

 dation of the Coal Measure seas over the same area. 



