the Geology of the North Coast of the St. Lawrence. 91 



ciable change appears to have taken place in the last 70 years. Whenever excavations have been 

 made in the sand, sufficiently deep to reach below the level of the sea at low water, clay has been 

 met with. In this respect, therefore, these undoubtedly alluvial formations bear a strong resem- 

 blance to the deposits in the valleys, basins, and hollows of the granitic hills previously mentioned, 

 and seem to differ from them principally in being much thinner, and in occupying lower levels. 



The sandy country continues from the Seven Islands to the river Moisic, 

 a large stream which is full of sand banks^ and deposits extensive sandy shoals 

 near its mouth. It is about five leagues from the Seven Islands. About three 

 leagues further eastward, the granitic hills, which to the westward range 

 several miles in rear of the coast, and opposite the islands attain an elevation 

 of 1700 feet, again approach the sea, and form the coast to the Magpie 

 river, a distance of 60 miles. 



4, The unstratified rocks of this long line of coast are arranged irregularly, 

 in round-backed hills and ridges, often studded thickly with round knolls. 

 Their elevation above the sea seldom exceeds 1000 feet, being about the same 

 as that of the coast westward of Pointe de Monts, There is a much greater 

 variety in the primitive rocks in this part of the north coast, than in any other 

 further to the westward. Besides the genuine granite, composed of quartz, 

 felspar, and mica, and considered comparatively rare in Canada, there is a 

 peculiar kind of glassy felspar*, not met with by us elsewhere, which forms 

 considerable hills and the coast for many miles. Porphyry was found at 

 the falls of the Manitou river, and I believe this is the only locality yet ob- 

 served in. Lower Canada : it passes into syenite. Magnetic iron ore occurs 

 abundantly in veins and beds, associated with the felspar rocksf . 



5. From the Magpie river to Mingan, the coast is formed of the stratified, 

 argillaceous, and arenaceous deposits, and of the alluvion of the river St. 

 John. The soil is poor, loose, and sandy, but covered with a dense forest of 

 spruce, with a few birch and aspen trees. 



Near the river St. John, resting on the clay, is a semi-indurated sandstone 

 in process of forming, by the percolation through the sand, of water strongly 

 impregnated with red oxide of iron. 



As my remarks have arrived near the western extremity of the Mingan islands, I shall make 

 a few observations upon the coast which has passed in such brief review. Our boats visited 

 every part, and ascended the rivers to their falls, yet no rocks of the transition or secondary 

 classes were observed in situ. Magnetic iron ore is largely and generally disseminated, although 



* I do not affirm that this is the glassy felspar of mineralogists ; but its cross fracture is highly 

 vitreous. Its laminae are frequently striated, — a character common in the felspars of the St. 

 Lawrence. 



t Most of the specimens in this section of the coast, were collected by my assistants Lieutenant 

 Collins and Mr. Bowen. 



n2 



