184 



and crosses the glacial boundary near Brownstowu, Jackson County. It 

 cuts across the unglaclated area in a west-southwest direction, and is 

 cut to a comparatively low gradient, although it has cut through many 

 rock formations of great hardness. The valley has been filled to such an 

 extent that the present stream is on the average about 100 feet above 

 rock floor. The bluffs are 200 to 300 feet above the present valley floor, 

 thus giving the preglacial valley a depth of 300 to 400 feet. In the un- 

 glaclated area the east fork receives only one important tributary from 

 the north, that is Salt Creek. Tliis creek lies wholly in unglnciated area 

 hut probably carried nuich water I'nun the melting heads of glaciers 

 wliich passed through tiie divides ti» the imrtheast. as is evidenced by the 

 filliiiir of s;iii(i and gravel in the upiier cimrse of the triliutaries, as ex- 

 iiiiiplc Iliihli.-ird's Ciij), Monroe ('ounty and cnstcni part of lirown County. 

 The streams leading down from these gajis iiavc strewn along their courses 

 glacial boulders of considerable size. 



In the Salt Creek basin the valleys are cut to great deptli and a 

 dendritic system of drainage lias been developed which stands out in con- 

 trast to the irregular and unsyinmetrical drainage system of the streams 

 within the dril't area to tlu' nortli and east. 



Lof<t h'ircr, an eastern triliutary to east fork, is entirely out of drift 

 limits area and for a distance of 12-ir) miles flr)ws through a subterranean 

 channel. In llnod limes [lart of tlie wnter tiows over the old surface l)e<l. 



TIk Mu sea I (if lick, a lai'ge triluitary from the east, has little fall 

 compared with the neighboring part of the east fork. At the railway 

 crossing soutii of Seymour tlie lied of tlu' Muscatatucic is forty feet lower 

 than at the crossing on the east fork to the north of Seymour. The dif- 

 f(>rence is due to a filling of the east fork valley by deposits of gravel 

 from the Wisconsin glacier. 'I'iie .Mnscatntuck lies outside of the Wiscon- 

 sin drift lindts ;ind the rea<'h of its waters and the vnlley reni;iins nu- 

 ll lied. 



The principMl trilmlaries of east foi-k to the northeast are Blue River 

 and Little Flat Rock Creek. These tributaries have an average fall of 

 about five feet per mile. From Columbus near the edge of the Wisconsin 

 drift to the mouth of the Muscatatuck the fall is about twenty inches per 

 mile. In the old preglacial valley through the driftless area the fall is 

 about ten inches per mile. Riffles and rapids in this part of the course, 

 however, increase the fall. The Iliudostan Falls below Shoals give a 



