74 



or four days, a thunder storm comes from the west, generally in the 

 night ; the south wind often blowing a hurricane all the time the storm 

 is approaching from the west. This storm is again succeeded by cool 

 weather and a high state of the barometer, and in general we found a 

 sure indication of the approach or termination of a storm in the fall- 

 ing or rising of the barometric column. These storms as seen on the 

 prairie have a number of independent centres, so that they often pass 

 ■across the landscape to the north and south without your receiving 

 any of the rain. They are frequently accompanied by a fall of hail 

 and violent gusts of wind. 



CHAPTER IV. 



Description of principal rivers and discussion of the merits of different 



routes. 



In giving a description of the character and importance of the rivers 

 examined, it will perhaps be best to discuss at the same time the sub- 

 ject of routes, as they are intimately connected. 



The Missouri, therefore, claims our first attention, and though it 

 has been so repeatedly described by others, a few of its general features 

 may be enumerated here. A detailed account of the various points we 

 examined as locations for military posts must be reserved for the final 

 report. This great stream has generally a uniform width from the 

 junction with the Yellowstone to its mouth, varying from ^ to ^ a 

 mile when the banks are full. In low water the width is much less 

 and dry bars of sand occupy portions of the bed, from which the water 

 has withdrawn. In the upper part of the river where the trees do not 

 destroy the force of the wind, the sand is blown about in the most 

 astonishing manner, and the clouds of sand can be seen for many 

 miles. Sand banks are thus formed, generally at the edges of the trees 

 on the islands and points, and which are often many feet above the 

 level of the highest floods. 



The force of these winds may be inferred from this, and from their 

 constancy during certain months, especially in October, are of them- 

 selves one of the greatest obstacles to the navigation of the river. 



The plans which these sand banks exhibit are those of the perime- 

 ters of the islands and points on which they were formed, and not un- 

 like those of the Indian mounds in the Mississippi valley, which are 

 supposed to be the remains of ancient fortifications. These banks along 

 the Missouri have, therefore, been considered as the works of the 

 aborigines, such, for instance, as those described and figured by 

 Lewis and Clark, as existing at Bon Homme island. I have con- 

 clusive evidence, from personal examination, that these were formed by 

 the wind, and are not the work of the ancient Toltecs as some writers 

 have supposed. 



The river has generally, in the same stages of the floods, about as 

 good navigation on account of the depth above James river as it has 



