482 PLEISTOCENE OF INDIANA AND MICHIGAN. 



and thus induce deposition of sediment and build up the banks. The Bassett Channel was 

 evidently once of large dimensions and is still in piocess of contraction. 



FRONT OF THE OLD DELTA. 



Another evidence of greater age in the eastern part of the delta is its lack of long ragged 

 levees along the outer parts of its old channels. Some ragged points are associated with the 

 Johnston and Ecarte channels, but they appear to be battered fading forms. None accompany 

 the Blind Channel, and only two or three fading remnants border the Bassett Channel. The 

 whole land front of the old delta has been much smoothed as compared with that of the new. 



RECENT AND PROGRESSING CHANGES IN THE CHANNELS. 



The aging or extinction of the older channels suggests the future of some of the newer ones. 

 The present active channels are not all in the same condition. One is aggressively active, 

 actually enlarging, and others are evidently dwindling. 



Throughout its whole length the North Channel seems to have the strongest flow. It is 

 on the average slightly deeper and wider than the South Channel and is the master stream and 

 would be the best route for navigation if it extended in a southwesterly direction. It seems 

 certain that until recently its waters followed the Chenal a Bout Bond, which is lined with 

 ragged levees as large as those of either the Middle or South channels, but which has so dwindled 

 in recent times that its deeper bed is now narrow and is bordered by wide shallows. It is not 

 very long since the bank between Point aux Trembles (where the main line of the North Chamiel 

 turns northwest) and the North Channel clubhouse was continuous across the present North 

 Channel or was broken by only a small crevasse. But some circumstance, perhaps an ice jam 

 like that which Cole describes as affecting the river higher up, forced a powerful current through 

 it to the northwest and established a new route. This part is so new that it has not yet built 

 any levees along its sides, those on the two sides near the clubhouse being parts of the older levee. 



The Middle Channel, which branches from the Noith Channel 2\ miles west of Algonac, 

 is also dwindling but has not shrunk so much as the Chenal a Bout Rond. The South Channel 

 has also dwindled and is now distinctly second in importance to the North Channel. Under present 

 conditions the North Channel has a decided advantage over the other channels and is evidently 

 gaining on them, for from the head of Russell Island to the open water of Lake St. Clair a quarter 

 of a mile northwest of Point aux Trembles, the distance is 3 miles shorter than to the open 

 water at the Old clubhouse on the South Channel.. It is characteristic for delta distributaries 

 to change and shift about, and just now the North Channel seems to be robbing the others. 



If the South Channel is to continue to be the mam route of navigation steps ought to be taken 

 to prevent its further dwindling if not to enlarge and improve it. This could be done by diversion 

 works above Algonac so arranged as to guide into it a larger proportion of the river. 



No doubt there was a small natural crevasse near Point aux Trembles before the main 

 cm-rent broke through, and this probably determined in part the course of the scouring current 

 at that time. Artificial cuts through the natural levee, such as have been made at many places 

 in the flats above the ship canal, are a menace to the maintenance of the deep channel. By 

 drawing off the water they slacken the flow in the channel and tend to increase deposition of 

 sediment. 



AGE OF THE DELTA. 



The muck beds described by Cole appear to rest on the surface of the lake clay which under- 

 lies the whole region. The muck evidently dates from one of the times when the upper lakes 

 were discharging eastward by other outlets and St. Clair River ran dry. Under the muck, Cole 

 generally found 2 or 3 feet of tougher clay marking the upper part of the lake clays. This 

 tough stratum appears to be an old land surface and was generally present, even where the 

 muck was absent. 



