No. 2.] ' DAWSON — POST-PLIOCENE. 181 



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, w^here some of the val- 

 leys 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 con- 

 tinuous sheet spreading over the surface. They occur in mounds 

 and lono: ridges, or eskers, 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 eiirht miles it forms a natural road. rouo;h in- 

 deed, 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 Cobe- 

 quid mountains to a ridge of sandstone that crosses the lower part 

 of the Hebert river. It consists of o-ravel and sand, whether 

 stratified or not I could not ascertain, with a few large boulders. 

 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. Shorter and more interrupted ridges of this kind may 

 also be seen in the country Northward and Eastward of the town 

 of Pictou. In sections they are seen to be stratified, and they 

 generally occur on low or level tracts, and in places where if the 

 country were submerged, the surf or marine currents and tides 

 might be expected to throw up ridges. The presence of boulders 

 shows that ice grounded on these ridges, and it, probably by its 

 pressure, in some instances, modified their forms. These eskers, 

 or " horse-backs," must not, however, be confounded with glacier 

 moraines, to which in structure they bear no resemblance what- 

 ever. 



D* 



