10 DIMINISHED FLOW OF EOCK RIVER. 



little time and forethought. It is in order to show this to practical 

 farmers that the latter part of this report has been prepared, and it is 

 earnestly hoped that it will receive the careful attention of those who 

 are interested in bettering themselves, but have not as yet given much 

 thought to the possibilities of the woodlot, which is, after all, so impor- 

 tant a part of a good farm. 



EXTENT AND TOPOGRAPHY OF THE ROCK RIVER WATERSHED. 



The headwaters of the Rock River are situated at the lower end of 

 a depression that extends from Green Bay and Lake Winnebago 

 southwestward toward the southern boundary of Wisconsin. (PI. I.) 

 Near that boundary the valley is interrupted b} T the glacial drift of a 

 moraine, known as the " Potash Kettle" or "Pots and Kettle Range. " 

 Throughout a part of this extent this range forms the eastern bound- 

 ary of the upper drainage basin of the Rock River. A series of 

 ledges and cliffs extend along the western side of the Kettle Range, 

 and overlook the extreme northern sources of the river. The drain- 

 age basin itself is confined on the northern side by a watershed that 

 separates the St. Lawrence from the Mississippi River Basin, and 

 divides the depression of southeastern Wisconsin into an upper and a 

 lower section. 



The greatest length of the Rock River Basin in Wisconsin is 85, and 

 its greatest breadth 65 miles. The area of the basin is 3,635 square 

 miles/' and is included almost entirely within five counties. The sur- 

 face is moderately hilly; it varies in elevation from 750 feet where 

 the river enters the State of Illinois, to 1,100 feet on the crests of 

 the Kettle Range. The rise from the interior of the valley is gradual, 

 and usually the hilltops are not more than 100 feet above the inter- 

 vening valleys, with an average slope of about 3 degrees. This 

 low, uneven topography has led to the formation of an intricate trib- 

 utary system (PI. II), with numerous spring-fed lakes, which, under 

 ordinary circumstances, furnish excellent means for an ample water 

 supply. (PI. Ill, figs. 1 and 2.) 



The fall of the river from Horicon Marsh, at the north, to the city 

 of Beloit, at the Wisconsin State line, is only 135 feet. This moderate 

 descent continues until the Mississippi is reached at an altitude of 510 

 feet, or 210 feet below that of Beloit. An account of this lower part 

 of the Rock River is omitted for the reason that its tributary system is 

 comparatively insignificant. 



"Geology of Wisconsin, Vol. II, p. 171. 



