xli 



the outside or on top of a bar, the banks will be found to be very sandy, 

 having no coherence, and mouldering away at the slightest touch ; but if 

 the deposit has taken place behind or on the lower side of a bar, the bank 

 has a greater tenacity and resists abrasion until undermined by the cur- 

 rent, and falling over is broken up and swept away. If the deposit has 

 been formed in an old cut-oft", it becomes, above the mouth of the Arkan- 

 sas and on the east side all the way down, stiff" tenacious blue-black clay; 

 but on the west side, after passing the mouth of the Arkansas, we fre- 

 quently find it mixed with the red deposits of that river. At several places 

 below the Arkansas there is a stiff" clay formation, particularly at Cypress 

 Bend, 25 miles below the mouth of the Arkansas, and in Yellow Bend, 10 

 miles below that, on the same (west) side; but this clay bank has fre- 

 quently branches and logs imbedded in it. This blue clay, as well as the 

 yellow, makes a more permanent bank than the more sandy, and better 

 resists the action of the current. The sandbars are mostly formed under 

 points where the current is slack, and are composed of the sediment 

 brought by the current from above and deposited in the slack current. 



Occasionally, a sandbar is formed in the middle where the river is wide, 

 and if the conditions are favorable the sandbar becomes a towhead — a 

 sandbar with young cottonwoods or willows — and eventually an island. 

 The sandbar formed under the point is increased every high water hy the 

 silt, and either willow or cottonwood takes root and covers the higher 

 parts with a dense carpet of verdure. After vegetation has begun, the 

 building of the bar goes on with increased rapidity ; for in addition to the 

 increased deposit of silt during high water, there is added, when the river 

 recedes in the summer, the action of the wind. When the wind comes 

 from a favorable direction, it lifts the sand from the more exposed parts 

 of the bar, and deposits it among the young growth on the higher parts; 

 and again, when the wind comes from an opposite direction, it brings the 

 leaves gathered from the forests behind, which add to the mass, and thus, 

 alternately, the wind deposits either sand or leaves, and the annual high 

 water, adding its silt, solidifies the mass until it reaches high water, and 

 then the wind continues the process. 



Again, another element comes in to increase the eff"ect : this is the cut- 

 off. These cut-offs are caused by the current cutting across a narrow neck 

 of land, causing the current and channel to leave its former bed and 

 take a new direction, frequently shortening the river ten or fifteen, and 

 in some cases as much as thirty miles. The effect of these cut-off"s is to 

 lower the bed of the river, immediately above, about three inches (depend- 

 ing on the slope of the river) to the mile. This lowering is gradually 

 lessened as we recede from the cut-oft" up stream. The effect below the 

 cut-off is the reverse of what it is above. If the cut-off takes place close 

 under a point where the wind has been raising the bar to or above high 

 -water, we shall find a bank from two to four feet above high water level. 

 These cut-offs are becoming more frequent as the banks become denuded 

 of timber. 



The following places illustrate the eft'ect of wind alone in raising the 



