TYRE-UBLY OUTLET. 41 



channel, on the east side, one mile south of the bend. Two other smaller 

 branch outlet channels cross cols about two miles east and southeast of 

 Tyre. At this place they unite and pass thence as one channel close to 

 Ubly on the south, and join the Ubly channel at a point a mile or more 

 below the latter place. Tyre is about four miles southeast of Ubly and 

 is also on the channel floor. Both channels possess distinct characters 

 of water-courses. The Tyre channel is a bouldery swamp for some dis- 

 tance above the town, and at the station there is scarcely any covering 

 over the underlying sandstone. The strata are bare in many places and 

 the thin soil is very gravelly and stony. The Ubly channel is floored 

 almost entirely with beds of gravel above the junction of the branches. 

 Boulders are numerous in some places, as on the east side a little below 

 the bend, one mile north of Ubly. The gravels were observed at several 

 places to be at least four or five feet deep. Below the bend the width of 

 the channel increases to three-fourths of a mile to a mile, and keeps this 

 width to Cass City. From the junction the floor of the channel is cov- 

 ered with great numbers of boulders for most of the distance down to its 

 lower end. The bouldery floor, nearly a mile wide, is well displayed at 

 Holbrook, about half way down from Ubly. The floor a mile and a half 

 east of Cass City has an altitude of about 730 feet. In its present atti- 

 tude the floor descends about 70 feet from the col east of Ubly to Cass 

 City, about 22 miles, but the descent of the water surface was probably 

 somewhat less. 



Cass City is built upon a gravel plain about two miles long east-and- 

 west and nearly a mile wide, which from its position strongly suggests 

 that it may be a delta of the outlet of lake Whittlesey. Its top level is 

 about 750 feet above sealevel or 20 to 25 feet above the old channel 

 bottom. There appeared to be a fragment of the same plain on the south 

 side of the river also, as though the original deposit had been cut in two. 



PORT HURON-SAGINAW MORAINE. 



The contemporary position of the ice-front with respect to this outlet 

 is very clearly marked. The last land-laid moraine of the Huron lobe 

 of the ice-sheet lies close to the east side of Black river all the way north- 

 ward from a point six or eight miles northwest of Port Huron. Where 

 the Black River swamp is wide the main crest of the moraine is some- 

 times four or five mile3 from the river, but it is usually half that distance 

 or less. The moraine is usually dual or triple in form, with two or three 

 crests or ridges running roughly parallel half a mile to a mile and a half 

 apart, the western one being the highest. Toward Ubly the moraine 

 trends northwest, and at a point about three miles northeast of Ubly it 

 meets the contemporary moraine of the Saginaw lobe coming from the 



