208 Geology of the Lakes and the Valley of the Mississippi. 



ity, the country between the lakes and the Ohio, is manifestly dilu-" 

 vial, consisting of flat beds of sand, clay, gravel and mud, without a 

 single rock, in situ, but with innumerable boulders of sienite imbedded 

 or lying on the surface, but more commonly huddled together in the 

 gullies and water-courses. They dissappear only as the country be- 

 comes broken by the incipient undulations ofthe Alleghany Mountains. 

 They vary in the proportions of their constituents from nearly pure 

 hornblende to feldspar porphryry, the feldspar, frequently verging on 

 flesh red. That they have been rounded in a long transport, only 

 a few of the larger being angular, is sufficiently attested by their ap- 

 pearance ; and that the tertiary, chalk, and oolite have been abraid- 

 ed by the tide that brought them, or else that it occurred at a period, 

 anterior to the deposits of these formations elswhere, is as plain as any 

 o;eological truth can be. There are two things which indicate with 

 a great degree of certainty, the quarter whence this current proceeded 

 and the points to which it was distributed. These are the nature of 

 of the debris scattered along its paths ; and the paths themselves in 

 their original state, or, as they now appear, deepened and contracted 

 by the fresh water streams. The crystalline structure of these de- 

 bris, consisting of granite, gneiss, hornblende, sienite, porphyry, agate, 

 jasper, quartz and other promordial substances, proves incontestably, 

 that they have come from a primitive region and not, as has been 

 generally but gratuitously assumed, from the north, where primitive 

 or volcanic rocks are not known to exist. In the lateral channels 

 and fresh-water lakes, we behold the footsteps of the agent that 

 brought them ; and by these we are able to track him home. The 

 present basins are but the remaining, as they were the deepest, parts 

 of the ancient channels. Why have we these basins ? Not as res- 

 ervoirs for a present superflux of water; for that might as readily be 

 disposed of by a trough of equal dimensions throughout the tract. 

 In fact the entire product of the rains that fall in the noihwestern 

 quarter ofthe continent, is passed by a succession of such troughs, the 

 intermediate links in the chain of lakes. We have the basins not 

 because we have an accumulation ; but we have an accumulation 

 because we have the basins. They evidently owe their excavation 

 to some other power than that of the waters which now possess them ; 

 and to what other are they so likely to owe it as to that of the great 

 denuding current of which we every where see such convincing 

 proofs ? To account for their origin at all, we must believe that 

 they were scooped out by it, the abrasions of the lias being but par- 



