6. Sketch of the Geology of the Arctic: Regions. 
bly gravel consisting of green felspar, white quartz, chert and lime- 
stone. These hills gradually diminish in altitude, and the eastern 
branch of the river runs round their northern limit in lat. 69°. White 
spruce grows as far as 68° where it disappears. The country thence 
becomes a frozen morass, onward, north of the hills, seldom thawing 
more than six or eight inches upon the surface. 
Alluvial Islands. 
‘The space occupied by the various reaches of the McKenzie be- 
tween the Rocky Mountains and the Reindeer Hills, is ninety miles 
in length, and from forty to fifty wide. The river forms this tract 
into islands, by the numerous channels through which it winds its way 
to the sea. The islands are most of them flooded in the spring, but 
annual accumulations of drift wood and sand, have raised some parts 
above the reach of the annual inundations, ‘and as far north as 68°, 
the highest parts are clothed in summer with dwarf willows, and white 
spruce. _ Sandy shoals skirt the coast, “ and the whole line from Cape 
Bathurst, in W. long. 127° as far west as the Sacred Islands in 
W. long. 137°, presents a striking similarity of outline and structure.” 
The sea coasts east of the McKenzie for many miles, are low, 
with occasionally, gently swelling sand hills. ‘The beaches and capes 
are thickly sown with fragments and pebbles of limestones, red and 
white sandstone, and sienite. Some of the promontories consist of 
bluish slaty clay, with a greasy feel, compact enough to be called 
stone, but crumbling readily in water. The cliffs are often variega- 
ted with beautiful colors. The shale is brown, interspersed with 
crystals of selenite, and between the leaves is filled with powdery 
alum mixed with sulphur. The wax colored variety of alum, called 
Rock Butter, occurs in layers, the shale is covered by “a bed of poor 
calcareous clay ironstone, which has a straight cleavage, and is 
coated by fibrous calc sinter, and chalcedony.” ‘The soil is clayey, 
and almost without vegetation. Further east in a high cliff of alum 
shale, alternating layers of Rock Butter occur again, with crystals of 
selenite on the surface of the shale. “ Pebbles of granite, sienite, * 
quartz, lydian stone, and compact limestone, all coated by white pow- 
dery marl” rest on the surface of the cliff. 
