82 THE POST-PLIOCENE PERIOD. 



comparative hardness and great mass, forms a liigli ridge extending 

 from the hill behind New Glasgow across the East and Middle Rivers, 

 and along the south side of the West River, and then, crossing the 

 West River, re-appears in Roger's Hill. The valleys of these three 

 rivers have been cut through this bed, and the material thus removed 

 has been heaped up in hillocks and beds of gravel, along the banks of 

 the streams, on the side toward which the water now flows, which 

 happens to be the north and north-east. Accordingly, along the 

 course of the Albion Mines Railway and the lower parts of the 

 Middle and West Rivers, these gravel beds are everywhere exposed 

 in the road-cuttings, and may in some places be seen to rest on the 

 boulder clay, showing that the cutting of these valleys was completed 

 after the drift was produced. Similar instances of the connexion of 

 gravel with conglomerate occur near Antigonish, and on the sides of 

 the Cobequid Mountains, where some of the valleys have at their 

 southern entrances immense tongues of gravel extending out into the 

 plain, as if currents of enormous volume had swept through them from 

 north to south. 



The stratified gravels do not, like the older drift, form a continuous 

 sheet spreading over the surface. They occur in mounds and long 

 ridges, sometimes extending for miles over the country. One of the 

 most remarkable of these ridges is the " Boar's Back," which runs 

 along the west side of the Hebert River in Cumberland. It is a 

 narrow ridge, perhaps from ten to twenty feet in height, and cut across 

 in several places by the channels of small brooks. The ground on 

 either side appears low and flat. For eight miles it forms a natural 

 road, rough indeed, but practicable, with care, to a carriage, the general 

 direction being nearly north and south. What its extent or course 

 may be beyond the points where the road enters on and leaves it, I 

 do not know ; but it appears to extend from the base of the Cobequid 

 Mountains to a ridge of sandstone that crosses the lower part of the 

 Hebert River. It consists of gravel and sand, whether stratified or 

 not I could not ascertain, with a few large boulder-stones. Another 

 very singular ridge of this kind is that running along the west side 

 of Clyde River in Shelburne county. This ridge is higher than that 

 on Hebert River, but, like it, extends parallel to the river, and forms 

 a natural road, improved by art in such a manner as to be a very 

 tolerable highway. Along a great part of its course it is separated 

 from the river by a low alluvial flat, and on the land side a swamp 

 intervenes between it and the higher ground. These may serve as 

 illustrations of the "boars' backs" or "horse backs" and gravel 

 ridges which occur in many other places, and are sometimes accom- 



