APPENDIX. 811 



the margin of the lake, extending by Thunder Bay and Presque 

 Isle, and the Isles of Bois Blanc and Round Island to Michili- 

 mackinac. At Thunder Bay, the compact limestone of the Saga- 

 naw Islands reappears, and is constantly in sight from this point 

 to Presque Isle, It exists in connection with bituminous shale, 

 at an island in Thunder Bay. It is of a dark carbonaceous cha- 

 racter on the main opposite Middle Island, at a point which is 

 called by the Indians Sho-sJio-nd-hi-lai-king^ or Place of the Smooth 

 Eock. I noticed at this point the cyathophyllum helianthoides 

 in abundance, and easily detached them from the rock. The more 

 compact portions of this formation in the approach to Presque 

 Isle, disclosed the ammonite, two species of the gorgonia, and the 

 fragment of a species of chambered shell, whose character is inde- 

 terminate. 



Much of the coast was footed, as the winds were adverse, and 

 its debris thus subjected to a careful scrutiny. Wherever the 

 limestone was broken up or receded from the water, long lines of 

 yellow beach-sand and lake-gravel, including members of the 

 erratic block stratum, intervened. In some localities, local beds 

 of iron sand occur. 



MiCHiLiMACKiNAC* — The approach to this island was screened 

 from our view by the woody shores and forests of Bois Blanc, an 

 island of some twelve miles in length lying off" the main land ; 

 and the view of it first burst upon us in the narrow channel be- 

 tween it and Eound Island. It is a striking geological monument 

 of mutations. Here the calcareous rock, which had before exhi- 

 bited itself in low ledges along the shore is piled up in masses, 

 which reach an extreme altitude of three hundred and twelve 

 feet. About two hundred feet of this elevation is precipitous on 

 its south, east, and west edge. A hundred feet or more is piled 

 up on its centre, part rock and part soil, in a crowning shape. 

 The highest part of this apex, which is surmounted by the ruins • 

 of Fort Holmes, consists of the drift stratum,. among which are 

 boulders of sienite, and other foreign rocks. A locality of these 

 abraded boulder-rocks, near the Dousman farm, is worthy of a visit 

 from all who take an interest in the phenomena of boulders dis- 



* The nume, as pronounced by the Indians, is Mich-en-i-mack-in-ong, meaning 

 Place of Turtle Spirits, a notion of their niytliology. It was anciently deemed a 

 sacred spot, or one where Monetoes revealed themselves. 



