484 PLEISTOCENE OF INDIANA AND MICHIGAN. 



Gravel and sand are constantly drifting southwest along the .Canadian shore into the head 

 of St. Clair River, where they have been deposited as a southward-pointing spit H miles long. 

 As the gravels were rolled into the opening the strong current swept away the finer particles and 

 dropped only the coarse material, adding layer after layer of coarse gravel to the westward front 

 of the spit, and constantly crowding the river over against its western bank. The current in the 

 rapids flows 4t miles an hour, and the relations show plainly that the existence of the latter is 

 due to the narrowing of the river caused by the growth of this gravel mass westward. 



On the American side there is no spit, but a much smaller bar or shoal appears farther 

 down the river. The west bank of the rapids has no protection against the swift current and is 

 eroded away as fast as the gravels on the east side press westward. Continual adjustment is in 

 progress and has been for a relatively long time, the river at Fort Gratiot having gnawed west- 

 ward into the clay land about a mile from its original position. 



The alignment of the Canadian shore of Lake Huron with reference to the head of the river 

 favors the formation of a spit, and that on the American side does not do so. Gravel carried 

 into the head of the river from the north on the American side is swept along the bottom of the 

 river, and probably added to the shoal off the mouth of Black River. It seems doubtful whether 

 much coarse gravel could be swept through the whole length of the river to the St. Clair delta. 



It seems probable, however, that the relative quantity of gravel brought in from the two 

 shores is much more important than their alignment. The Canadian shore faces west and north- 

 west and receives the full force of the heaviest storms. The Michigan shore faces east and is 

 not so severely attacked. Both shores have been heavily eroded in the past and are still receding, 

 but the length of shore tributary to the head of the river is considerably greater on the Canadian 

 side. Cole does not accept this explanation of the rapids in his report, but he looks at the matter 

 from a slightly different point of view. 



The gravel mass at Point Edward measures li miles from east to west and about 2 miles 

 from north to south. The deposit appears to be all of modern or post-Nipissing age. At the 

 time of Lake Algonquin the entrance to St. Clair River was a wide tapering bay opening north- 

 ward from Corunna; and the gravels of the Algonquin stage, except for one prominent bar upon 

 which the London road enters Sarnia, lie north and northeast of Sarnia and are quite separate 

 from those that have displaced the river at Point Edward. The deposits related to Lake 

 Algonquin have not been fully investigated. 



The Point Edward spit is the correlative of the new part of the St. Clair delta. Every north 

 or northwest storm cuts into the great clay cliffs on the Canadian shore, roils the water in the 

 shallows, and stirs up the gravel. The shore current bears the roily waters along and rolls the 

 gravel toward Point Edward. Once there they separate, the coarse materials and gravel being 

 added to the great spit and the fine sediments being carried down to Lake St. Clair and built 

 into the delta. The mam part of the spit has been built since the closing of the North Bay 

 outlet. The process has a peculiar international relation; the shores of Lake Huron on the 

 Canadian side are being torn away, and though the coarse material is mainly left at Point 

 Edward on the Canadian side, nearly all the fine sediment is carried down the river and built 

 into the new St. Clair delta on the American side. 



LAKE ST. CLAIR. 



The body of land which projects into the west side of Lake St. Clair on the two sides of Clin- 

 ton River looks like a delta on the map but is shown by Cole's investigations to be mainly glacial 

 till carrying bowlders — probably part of the Emmett moraine. Only about 800 acres of it along 

 the outer front is of the nature of a delta, and Black Creek, which flows southwaxd through it, 

 is the only distributary besides Clinton River that crosses it. 



Salt Creek, west of New Baltimore, and Swan Creek, west of Fair Haven, have produced 

 only very small salients in the shore line. 



