3i6 



Miles and area. The steep northern face of the upland ex- 



Kilometres. r • i t i i 



tends along a iairly unitorm northeast-southwest 

 course. To the northeast the upland finally 

 approaches the sea coast. In this direction, 

 in the Arisaig district, the northern face of the 

 upland marks a profound fault, presumably 

 this is true also to the southwest. The upland 

 in its extension both to the northeast and south- 

 west is mainly underlain by Ordovician strata 

 with large areas of igneous rocks. In places 

 also, Silurian measures are largely developed. 

 Where the railway, a short distance beyond 

 Avondale station, enters the Carboniferous 

 area, the strata belong to the Limestone series 

 and consist chiefly of grey and red sandstones 

 with, towards the base, several beds of lime- 

 stone. These measures, with low northeasterly 

 dips, form a zone several miles wide extending 

 in a northeasterly direction and in the immediate 

 district rest directly on the Silurian strata. 

 On the sea coast these rocks have a thickness 

 of about 2,000 feet (600 m.) and on fossiliferous 

 evidence have been correlated with the Windsor 

 series. 



At a distance of about i^ miles (2-4 km.) 

 from Avondale station, as the railway follows 

 along the southern boundary of the Carboni- 

 ferous at the foot of the upland of Ordovician, 

 it leaves the area of the Limestone series and 

 enters a district occupied by Millstone Grit 

 which at the south boundary rests directly on 

 the Pre-Carboniferous strata. The railway in 

 this part of its course, ascends a valley, crosses 

 a divide (altitude, 288 feet or 87-8 m.) and 

 enters the valley of Huggan brook. From the 

 neighborhood of the summit, a view to the 

 northeast shows the sharply marked, nearly 

 straight front of the upland of older strata 

 and the low, rolling Carboniferous area extend- 

 ing from its foot to the sea. 



23 m. Piedmont Station — Alt. 241 ft. (73-5 m.). 



37 km. The Millstone Grit strata in the neighborhood 

 of Piedmont station consist of grey and reddish 

 shaly sandstones with coal-like matter; the 



