168 
THE GEOLOGIST. 
rock (composed of the Niagara limestone), which projects into the 
lake from the lofty island which bears their name. On other parts of 
the coast the rock is still wearing away by the action of the waves 
into the same remarkable pillar-like shapes. Those which at present 
exist have been formed in a similar manner to the Flower Pots on 
the Mergan Islands, and the " Old Woman" of Gaspe, having at one 
time constituted caverns, as I have already described. 
10. — Perforations and Caverns of Michilimacinac Island, Lake 
Huron. 
The Island of Michilimacinac is situated near the straits of the 
same name, at the north-western part of Lake Hm'on, and is com- 
posed of gypsiferous limestone and rocks belonging to the Onondaga 
salt group of the American geologists. It is a hundred and fifty 
feet in height, and its precipitous cliffs are broken into a number of 
shallow and deep caverns by the action of the waves. One of these 
perforates a projecting point of rock near its south-east angle, and 
the general appearance of the coast is not dissimilar to that of the 
Pictured Rocks, presently to be described, only that they are not on 
such an extensive and grand scale. Besides these caverns, produced 
by aqueous agency, three objects of natm-al curiosity, are visited by 
strangers in this island — they are the Giant's Arch, the Natural 
Pyramid, or Sugar Loaf Rock, and the Skull Rock. The last of 
these is noted for the presence of a cavern, which would appear at 
one time to have been a place of ancient Indian sepulture, as num- 
bers of human bones were discovered within it, and are even now 
observed laying about its mouth. The entrance to the cavern is low 
and narrow, but its dimensions are not very considerable. It pos- 
sesses some historical interest for Canadians, from the fact that it 
was in this cavern that Alex. Henry was secreted by a friendly 
Indian after the massacre of the British garrison at Old Michili- 
macinac, in 1763.* 
11. — The Pictured Rocks, Lake Superior. 
These are included in the present paper, although in the territory 
of the United States, because they were celebrated among the French 
Voyageurs, who gave them the name of Les Portailles. The 
Pictured Rocks (as they are now best known) continue for twelve 
miles along the south coast of Lake Superior, about eighty miles 
west of White Fish Point. They consist of a series of lofty cliffs, 
varing in height, but mostly of three hundred feet, and are com- 
posed of horizontal stratified layers of grey sandstone, weathering of 
different tints, which are the equivalent of the Potsdam sandstone, 
a white quartz rock, probably overlaid here in some places by the 
calciferous sandstone. All along this coast the fury of the waves, 
* See Ileiu'y's Travels and Adventures. 
