30 llie American Geologist. January, 1895 
series of parallel beach ridges, in some places very distinct. 
This is especially the case where the bank is narrow. 
The high tract of Gros Cap is divided in two parts by an 
east-west valley, and the shore near the lake falls away to a 
low, sandy flat along its front. Towards the north the high 
ground ends near Obeshaw's corner, and the coast beyond is 
lower and sandy. A road across the hill eastward from the 
corner affords a short cut back to St. Ignace. But a mile or 
more of dangerous corduroy over a swamp to the east has the 
effect of lengthening rather than shortening the distance. 
The swamp was cut off from the lake by littoral drift near St. 
Ignace. The top of the high ground is substantiall}'^ flat and 
its altitude is about 160 feet. On the west edge there is a 
beach ridge much like that at 115 feet near St. Ignace, but 
not so well formed where we saw it. Much of the top is still 
in timber. But so far as we could see or learn by inquiry no 
part of it rises higher than that which we saw. Towards the 
southeast, Gros Cap is substantially continuous with the high 
irregular ground south of St. Ignace. On the northeast it is 
separated from high ground by a low trough one to two miles 
wide and occupied by swamps and ponds. The island of St. 
Helene, which lies about three miles off this shore in lake 
Michigan, is said to be a series of concentric gravel ridges. It 
is low, however, and probably does not attain a hight of more 
than 30 feet. There are many evidences of submergence along 
the line of the railroad northward from St. Ignace to and be- 
yond Trout lake. But none of them appear to record the up- 
per limit. The highest points observed were not over 260 
feet above lake Huron. 
Gros Cap and the other high parts near St. Ignace appear 
to have undergone the same severe wave action as Mackinac. 
They are all composed of a friable limestone which was an 
easy prey to the waves. On Mackinac the weakness of the 
rock is greatly increased by softer layers which weather into 
a fine fire-clay, as may be seen in the cliff' south of Arch rock. 
When the lake stood at a higher level, this clay collected in the 
rock crevices of the bottom along the shore and appears there 
to-day as a tough, buttery deposit, perfectly smooth in the 
fingers, and with two colors, red and greenish graj'. The 
