34 J 



GEOLOGICAL SURVEY OF CANADA. 



S»rface 



lee action. 



North Twin 

 Island. 



side, sand and clay greatly predominate; a cut bank one-quartet- of a 

 mile inland gradually rises to an elevation of forty feet near the south- 

 east point, with a lower raised beach of ten feet in front, the latter 

 composed of sand, the former of boulder clay. 



The interior of the island rises gradually towards the centre, where 

 it has an elevation of one hundred feet above the sea. 



Small lakes fill all the depressions on its surface. With the excep- 

 tion of some four or five stunted white spruce, less than ten feet high, 

 no trees grow on the island, which is everywhere covered with mosses 

 and arctic plants. 



A fine example of the expansive power of ice may be seen half a mile 

 inland from the south east point, where there is a small shallow lake, 

 at present completely drained by a 6mall stream, which has cut out a 

 channel through the escarpment. This old basin. is nearly round, 

 with a diameter of five hundred yards, and had a depth of about six 

 feet. Around the old shore lino is a bank of bouiders and clay, four 

 feet high and eight feet wide at the base, overgrown with vegetation, 

 and resembling the intrenchment of a fortified camp. This has evi- 

 dently been pushed up by the total freezing of the lake and the expan- 

 sion of the ice. 



Scattered over the surface of the island are great quantities of small 

 angular fragments of light yellowish fossilifcrous Silurian limestone, 

 the probable result of the breaking up of large boulders of the same. 



Separated by a channel five miles wide, and lying four miles to the 

 westward of this island, with its south-west'point in lat. 53° 04' is the 

 North Twin. Like the other island, it has an abrupt escarpment on 

 the east side, with a low shore line on the west rising slowly inland. 

 Prom the south-west point along the south side, the low shore is com- 

 posed of sand and gravel, with a wide margin of swampy land extend- 

 ing inland to the slowly rising interior. Low cut banks occur near the 

 coast at the south-east point, where two terraces of ten and thirty feet 

 elevation are seen, the lower formed of sand and gravel, the upper of 

 boulder clay and sand. 



On the east side is a wide shallow bay, with low swampy land from 

 a quarter to a half a mile inland to the base of a boulder clay escarp- 

 ment fifty feet high. On the northern part of the east side a low ter- 

 race, fifty feet high, composed of sandy clay, with a few boulders, rises 

 near high water mark, and extends inland on an averago a half mile 

 to a "second terrace thirty feet higher, and of similar composition. On 

 the north side the land adjoining the shore is made up of sandy dunes 

 dotted with boulders, rising slowly inland, with numerous boulder 

 points along shore. Along the west side the shore margin is low and 

 swampy, with sand and gravel beaches between boulder points, the 



