REPORT ON FIELD WORK IN GEOLOGY. I3I 



channel and widens its borders in the same manner. In this way 

 great valleys or embayin(3nts recede from the main stream for miles, 

 leaving promontories or liead lands between them projecting towards 

 the river. But the serrated and scalloped bluff now has many times 

 the surface exposed to the agents of destruction that it would have 

 were its walls straight. As the tributary valleys continue to widen 

 the promontories between them as continuously become narrower. 

 During all this time the protecting covering of limestone prevents the 

 height of the hills from being reduced, and should the broad valleys 

 gradually become deeper the hills actually increase in relative height, 

 although their elevation above the ocean may not increase. 



The river valleys of Kansas in general correspond to the above 

 description. The Kansas river, the Neosho river, the Verdigris river, 

 the Osage river, and many others, all are fashioned on this general 

 plan. If the reader will travel up or down the Kansas river between 

 Kansas City and Abilene he will be impressed not only with the 

 beauty of the scenery, but also by the oft repeated stencil-like recur- 

 rence of the same general features. A valley averaging four miles 

 wide has the ever widening stream meandering from bluff to bluff 

 always obedient to the laws of nature governing such flows. But the 

 bluffs are not continuous. Here a broad valley almost vying with its 

 parent in .width stretches away to the north, and there a similar one 

 extends to the south. But on either side their portals stands a lime- 

 stone clad promontory as though to guard the entrance to the garden 

 beyond, for the lateral valleys tridy are gardens and threshing floors. 

 Sometimes the tributaries will be miles apart, and the unbroken bluff 

 correspondingly long; at other places they will be close together so 

 that the highlands between are long and slender reminding one of 

 piers projecting into a lake or bay to protect a harbor. 



Should one explore either of the other streams mentioned he would 

 find substantially the same conditions produced by similar causes. 



But this mode of erosion is by no means confined to the areas 

 immediately adjacent to the water courses; for the whole surface of 

 the country is shaped under the same regulations. Figure i is a dia- 

 grammatic and condensed representation of the surface of eastern 

 Kansas, together with the peculiar properties of the rocky crust of 

 the earth at this place upon-which the contours depend. It repre- 

 sents a series of limestone systems approximately parallel dipping 

 gently to the west, and outcropping on a surface inclined towards the 

 east. The intervening spaces are filled with shale or other matter 

 which readily yields to erosion. The right hand limit of each lime- 

 stone system therefore is marked by a terrace nearly as high as the 

 distance downward to the next limestone; for, as already seen, the 



