820 APPENDIX. 



Stone, of little cohering power. The effect of waves beating upon 

 rocks is to communicate a curved line. This has operated to 

 excavate numerous and extensive caves into the coast. These, 

 after reaching hundreds of feet, have in some cases united. The 

 effect is to isolate portions of the coast, and to leave it in fearful 

 pinnacles, having many of the architectural characters of Gothic 

 or Doric ruins. 



The portion of coast immediately west of Grand Marrais is 

 scarcely less unique. It denotes the effect of the prostrating 

 power of the lake in another way. The sandstone of parts of 

 the coast, ground down into yellow sand by this vast machinery, 

 is lifted up by the winds as soon as it reaches the point of dry- 

 ness, and heaped up into vast dunes. Standing trees are buried 

 in these tempests of sand, and its effect is, for about nine miles 

 along the coast, to present, at an elevation of several hundred 

 feet, a scene of arid desolation, which can only be equalled by 

 the Arabic deserts. 



A dyke of trap seems once to have extended from the north 

 shore to Point Keweena; but, if so, it has been prostrated, and 

 its contents — veins and deposits, silicious and metallic — scattered 

 profusely around the shores of the lakes. A cause less general 

 is hardly sufficient to account for the wide distribution of frag- 

 ments of the copper veins and vein-stones which have so long 

 been noticed as characters of this lake. The basal remains of this 

 antique dyke form the peninsula of Keweena. The tempests 

 beating against this barrier from the northwest, have ripped up 

 terrific areas from the solid rock, and left its covering, amygda- 

 loid and rubblestones, in fantastic patches upon the more solid 

 parts, or constituting islands in front of them. 



Structure of its southern Coast. — The estimated distance 

 from Sault Ste. Marie to Fond du Lac is a fraction over 500 miles. 

 The sandstone, as it appears in the Falls of the St. Mary's, does 

 not appear to be entirely level. It exhibits an undulation of 

 about 8° or 10°, dipping to west-northwest. Two instances of 

 this waved stratification of the Lake Superior sandstone deserve 

 notice. The first terminates at the intersection of red sand rock 

 at la Point des Grande Sables with the beginning of the horizontal 

 strata of the Pictured Eocks. "We again observe an inclination 

 of the strata of a few degrees at Grand Island, which is more 



