114 Expedition to the 



soil and of rocky strata which formerly filled the space now 

 occupied by the immediate valley of the river, has been 

 removed by the Missouri. From the summit of the bluffs 

 there is a sloping ascent towards the interior of the country, 

 and it is probable the aggregate elevation of the great plains, 

 is not less than three hundred feet above the surface of the 

 river. If we admit that this great valley, with its numerous 

 ramifications, has resulted from the operation of currents, 

 wearing down, and transporting to the ocean the solid ma- 

 terials of the earth's surface, it would appear necessary st;ll 

 farther to acknowledge that this channel was once much deep- 

 er than at present, for we usually meet with thick alluvial 

 depositions covering the rocks that line the bottom of the 

 Missouri valley. The manifest tendency of the operation 

 of the Mississippi, at this time, upon its valley, is to fill up 

 rather than to excavate ; but it may be doubted whether this 

 is equally, or even to any degree, the case with the Missouri. 

 The aggregate mass of alluvion within the valley of the 

 Missouri is, undoubtedly, moving downwards, with con- 

 siderable rapidity, fojr the quantity of earthy matter carried 

 into the Mississippi is, at all times, very great. In their 

 descent the alluvial substances are alternately deposited and 

 swept away, as by the variations in the direction of the cur- 

 rent any particular point is, from time to time, either expos- 

 ed to, or sheltered from, the action of the stream. 



About eighty-seven miles above Cow Island is the mouth 

 of the Nodowa, a river of some importance, being about 

 seventy yards wide, and navigable to some distance. It is 

 not usually seen in passing, being concealed by the island 

 called the Great Nodowa, which is about five miles long, 

 and covered with heavy forests. The lands on tne Nodowa 

 are of an excellent quality. 



On the 1st of September, we were under the necessity of 

 remaining encamped near the mouth of Wolf river, that 

 some repairs might be made to the steam engine. Here we 

 sent out some persons to hunt, who after a short time re- 



