Wilson — Glaciation of Orford and Sutton Mts., Quebec. 199 



East of Orford ridge the lowest portion of a broad valley is 

 occupied by Lake Memphremagog, a long narrow lake which 

 receives a considerable amount of drainage from south of the 

 boundary. The waters of Lake Memphremagog pass out 

 northeastward by the Magog River — a tributary of the St. 

 Francis — and eventually reach the St. Lawrence River. On 

 the Orford ridge Mount Orford has an elevation of 2820 feet ; 

 Owl's Head, 2465 feet ; Hog's Back, Sugar Loaf, and Bear 

 Mountains are considerably lower. The lowest parts of the 

 transverse depressions on either side of Owl's Head stand at 

 elevations of about 1250 feet above sea level. Sutton Moun- 

 tain rises to 3120 feet, and the depression to the south through 

 which the Canadian Pacific railway runs has an elevation of 

 about 500 feet near Mansonville station. The Missisquoi River 

 at Richforcl, Vt. stands at 443 feet. St, Armand Pinnacle has 

 an elevation of over 2500 feet (Dresser). The surface of Lake 

 Memphremagog stands at 682 feet (Feb. 3, 1892) above sea 

 level. 



Character of the Surface of the Area. 



In the valleys the surface of the bed rock is usually buried 

 under a cover consisting of both modified and unmodified drift. 

 In a number of localities small outcrops showing striated sur- 

 faces are known. The directions of the striations indicate that 

 the general direction of the ice movement in the valley was 

 controlled by the structural trends of the valley sides. 



On the higher ridges even to the very summits a cover of 

 drift materials, more or less mingled with recent debris from 

 local sources, is found. The rock exposures are usually more 

 numerous than in the valleys, and the striated surfaces indicate 

 that the general direction of ice movement has been in a direc- 

 tion lying about thirty degrees to the east of south. 



Special localities. 



Orford Mountain. — The Orford ridge reaches its highest 

 elevation about twenty miles north of the International boun- 

 dary in the mass usually called Orford Mountain. The highest 

 point of the mountain is located on a rounded dome-like pro- 

 minence near the southern end of the local ridge that consti- 

 tutes the mountain. The summit of the dome is marked by a 

 small nearly level area a little less than a quarter of an acre in 

 extent. In detail this summit plain consists of low ridges of 

 trap with rounded contours, the general trend of these local 

 ridges being about S. 35° E. The hollows between these 

 small ridges are filled with loose debris which contains a few 

 fragments of the bed rock, but the greater portion of which 

 consists of material foreign to the mountain. The small bare 



