144 Wcoldridge on the ^iver=Lake Syetem of W. Mich. 
accompanying map, together with more cursory observations at 
various points from Grand Traverse bay to the mouth of the 
Grand river at Grand Haven, enables me to state the following 
facts regarding this system of lakes and the region where they 
are found. 
I St. These lakes assume the same form that would be pro- 
duced if they were covered by dams across the river valleys at 
/>! Cf.hrTo iiichiiU alt t/>e fentitres .!luwii,/ifustce(/enLokf 
<;.;,)'.'')• yu-iti'i!i/ .Tr plaw^ ntrtil eve w>(f too far nfr/h on this >niif>. 
there outlets. They are elongatedin the same general direction 
as the valleys of the streams which flov\' into them. They are 
deepest toward lake Michigan, they terminate, or begin, in 
marshes at their inland extremity, and they usually extend some 
distance into the valleys of tributary streams flowing into them. 
2nd. Their beds are excavated in the drift clay, and not in 
