DISPERSION OF ERRATICS. 
1V3 
ages almost everywhere scored and polished like the rocks 
which underlie a glacier. The discharge of ice into the sur¬ 
rounding sea will take place principally through the main 
valleys, although these are hidden from our sight. Erratic 
blocks and moraine matter will be dispersed somewhat irreg¬ 
ularly after reaching the sea, for not only will prevailing 
winds and marine currents govern the distribution of the 
drift, but the shape of the submerged area will have its influ¬ 
ence ; inasmuch as floating ice, laden with stones, will pass 
freely through deep water, while it will run aground where 
there are reefs and shallows. Some icebergs in Baffin’s Bay 
have been seen stranded on a bottom 1000 or even 1500 feet 
deep. In the course of ages such a sea-bed may become 
densely covered with transported matter, from which some 
of the adjoining greater depths may be free. If, as in West 
Greenland, the land is slowly sinking, a large extent of the 
bottom of the ocean will consist of rock polished and striated 
by-land-ice, and then overspread by mud and boulders de¬ 
tached from melting bergs. 
The mud, sand, and boulders thus let fall in still water 
must be exactly like the moraines of terrestrial glaciers, de¬ 
void of stratification and organic remains. But occasional¬ 
ly, on the outer side of such packs of stranded bergs, the 
waves and currents may cause the detached earthy and stony 
materials to be sorted according to size and weight before 
they reach the bottom, and to acquire a stratified arrange¬ 
ment. 
I have already alluded (p. 172) to the large quantity of 
ice, containing great blocks of stone, which is sometimes seen 
floating far from land, in the southern or Antarctic seas. 
After the emergence, therefore, of such a submarine area, 
the superficial detritus will have no necessary relation to the 
hills, valleys, and river-plains over which it will be scattered. 
Many a water-shed may intervene between the starting-point 
of each erratic or pebble and its final resting-place, and the 
only means of discovering the country from which it took 
its departure will consist in a careful comparison of its min¬ 
eral or fossil contents with those of the parent rocks. 
