ECOLOGICAL SU< CE--ION. 



and it will -iifln e, f"r our purposes, to state that the level of the 

 water fell to a poim al ut 40 feet above the present Lakr Michi- 

 gan. After -landing in this position for a time, ii fell again to 

 a point 20 feet lower. Its next period of standstill \\as at a 

 i2-toot le\el from which it receded to the proem lake level. 



The oldest of the north -hore -t reams probably began as mere 

 gullic- when the lake was al its 6o-foot level. These gullies have 

 \\-orked their way hack into the morain and deepened thcirchan- 

 neK in the manner described by Adam- '>! and diagram- 

 matically illustrated in Fig. i. Long ago Bull Creek was similar 

 to the pre-ent ( "oiinty Line Creek. At a recent period County 

 Line ( "reek v . liki- < il.-n <k. 



There ha\e liei-n -oine moilitH-atioiir, i if the-e j)r- caused 



l.\ i hair.. - ill lake level. Karh time the 1(\ el of the lake fell, the 

 -lriain-u. I \\iih portion near the mouth-. I'nder 



l-'i'.. -'. I >i. 1^:1. iinin.it n.irtli 



.in- m.i|i|.i-,! I tli<- ii. 



:lil<- ill til.' .'AH 



ill lutikrii liin--. \\hiili 1 hich exist m nature. 



,H.| tin.- top oi tiir diagram 



iHiinlii-i on tl ree <>t' tin- -m-am 



i -ont.iiii- fish. . 



tin- n-.l-lii-lls. tin.- I'lack-ii. -:thys 



<j/r,". ! minnow-; 5. tlio pifki-n-l ami lilunt-no-'-'l ininnou ; 



(>. tin- -iinti-li and l>.i-~; 7. the pike. chut'. ~uck '. i- about 



60 fret hi.uh. Tin- stipple.! :'.n iu~t al-cvc tl 1 the la',. 



