184 



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

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

 cut U> ;i c'liiipiiratively low gradient, although it has cut through many 

 rock forniatious of great hardness. Tlie 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 fcH't. In the un- 

 glaciated area the east fork receives only one important tributary from 

 the north, thafis Salt Creek. This creek lies wholly in unglnciated area 

 hill, proltably carried much water Irniu the melting heads of glaciers 

 which passed through the divides to the northeast, as is evidenced by the 

 filling of sand and gravel in the ui)per course (jf the tributaries, as ex- 

 .•im])]*' Iluliliard's Ca]), Monroe County and eastern part of Brown County. 

 The streams leading down from these gaps have strewn along their Cdurscs 

 glacial boulders of considerable size. 



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

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

 trast to the irregular and unsymmetrical drainage system of the streams 

 witliin tlie drift area to the north and east. 



Lost River, an eastern tributary to east fork, is entirely out of drift 

 limits area and for a distance of 12-1.") miles flows through a subterranean 

 chaimel. In flood times part of the water flows over the old surface bed. 



The MuscatatiicL-. a large tributary from the east, has little fall 

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

 crossing south of S(\vmour the i>c(l of the Muscatatuck is forty feet lower 

 than at th'' crossing on the e;ist fork to the north of Seymour. The dif- 

 Icrcncc is due to a filling of the e;ist fork valley by dei)osits of gravel 

 from the Wisconsin glacier, '{"lie Muscalatuck lies outside of llie Wiscon- 

 sin drill limits and tlie I'encji of its waters and llie \;illey renuiins iin- 

 lilled. 



Tlie iirincipal I riluilarics of e;ist fork to the nortlieast are lUue Kiver 

 and Little Fl.-it Itock Creek. Tlu'se tributaries li:i\(^ an aver.age fall of 

 about live U'('\ jier mile. From Colunibiis near the edge of tlie Wisconsin 

 i\r\f\ to the iiioiilli of the Alusc.-it ;it lick llie fall is about iweiily inches per 

 mile. In llie nld preghicial \alley tln-ough the driflless area the fall is 

 iiboiit ten indies per mile. Itilllcs and r.ipiils in tiiis jiart of the oiurse, 

 however, iiicrejise tile f;ill. 'llie lliiidnstaii I';ills iielow Slioiils giV(' ;i 



