April 3, 1876. 1 ^^^ [Price. 



Their slow, crawling motion and irresistible force ground the rocks to pow- 

 der, as wheat is ground to flour between the upper and nether mill-stones ; 

 not only ground them to powder, but rounded and polished the boulders and 

 the gravel, planed and grooved the rocky surface of the earth, and moved the 

 vast masses of drift materials from place to place in slow procession." 5-6. 

 " But the great mixing and transporting agency which arranged, assorted, 

 and deposited our Northern Illinois drift deposit, was evidently the mixed ac- 

 tion of ice and tcater." 6. The first and greatest force was the glaciers of the 

 high lands ; "then the floating iceberg and ice-field produced by their re- 

 sults, carrying the large boulders from place to place, and dropping them 

 over the ice-cold seas ; and last, the wave and current forces of water, after 

 the ice had in part, or altogether melted, left loose clays, sands and sub- 

 soils, substantially as we find them now." 6-7. " Eroding and denuding 

 influences have removed from three hundred to three hundred and fifty 

 feet of Magnesian limestone and shales." "The dynamical powers of 

 heavy bodies of water and water currents, and other drift forces, must 

 have acted long and powerfully in bringing them about." 31, and see 32. 

 "A mixed mass of gravel * * would seem to indicate that forces from a 

 distance and forces near at hand, operating in every conceivable direction, 

 with great force and over long periods of time, all contributed to gather to- 

 gether these heaps of abraided materials, some from the distant regions of 

 the granite and the traps, and some from the neighboring limestones of a b^'- 

 gone geological age ; but all equally worn smooth by the grinding of the waters 

 and ice. "109. " Whether the floating iceberg, or the slow crawling glacier, 

 or the strong water currents, or all these combined, transported the coarser 

 materials of the drift, the force of the powerful agents were much modi- 

 fied in their action here." 145. It would seem that the other powerful 

 causes stated, might suffice, if "the slow crawling glacier were omitted ; 

 and this is the opinion of Mr. E. B. Andrews ; assistant in the Ohio Survey, 

 2 Vol. 447. He says, " There is no general planing off" of the rocks ; but 

 everywhere among the hills where the northern boulders are most abund- 

 ant are projecting knobs or outliers of soft rocks, which would naturall}^ 

 be an easy prey to such a destructive force as would be exerted by the 

 movement of a vast glacier." 448. 



Moving westward we reach "Wisconsin, Iowa and Minnesota, upon whicli 

 David Dale Owen made his Geological Report, to the U. S. Govern- 

 ment in 1853. Among the materials of the drift the "trappean rocks are 

 much the most common." " They originated at the time of the upheaval 

 of the trap, and at comparatively a recent period. There are facts ascer- 

 tained which render it probable that a large area of the Northwest Terri- 

 tory has been raised during very modern periods, even since the present 

 fauna inhabited its rivers and lakes." "There is a gradual drainage of 

 its waters taking place, even at this time." p. 143. 



"In the vast prairie region of Iowa, the attention of the geologist is 

 frequently arrested by erratic blocks of enormous dimensions, scattered 

 here and there, and half sunk in the ground." " They are far from their 



