60 
from the Baltic, and bodily passed over the whole of Scotland, 
Western Islands and all, after filling up the Minch — slipping over 
the whole land like the bedclotlrcs slipping over a sleeping man. 
This theory admits of the after-effects of local glaciers — the 
dwindling residues of the enormous mass. 
Ihe second theory is based upon the Gulf Stream having at one 
period pursued a directly northern course, up the depressed valley 
ot the Mississippi, and down the IMackenzie Biver, so as to impinge 
upon Banks’ land, and, by the genial influence of its tepid waters, 
siqjply the necessary Avarmth to the plants which furnished the 
coal Avhich there occurs. Then the cold current from Baffin’s Bay 
and the North would bear a great ice sheet to grind and tear itself 
against our western shores — bear off their shattered fragments upon 
its flanks and shoulders — carry them in its oiiAvard course up and 
among the fiords and passes of our hills and valleys, shedding its 
burden from off the fringes of its .shrivelling bulk. 
The ihinl theory differs not widely from the last, but regards 
the greater amount of the ice work of the central heights as havin" 
been effected by material of home gi'owih. Maintains tliat the 
absence of the lieating Gulf Stream from our western shores had 
given us the climate normal to our latitude, namely, that of Labrador. 
That our hills supplied the neve Avhich formed our native glaciers, 
Avhich passed naturally and normally down every valley Avliich 
radiated from tlio central parent-height. But that simultaneously, 
or upon an after-depression of the land, ice-floes were borne from the 
north and west ; and, pressed by tlie vis a tergo of a continually 
advancing sheet, slid over the loAver grounds, or the sinking land — ■ 
accounting for the more general but less })rofound action Avhich 
is there disclosed. 
It is to be noted, that each of the three theories alike puts the 
question — In luhat direction did ihe ice pass over the western 
shores f The first theory demands that it passed /ro?n east to ivest, 
both of the others that it passed from vorih-ivesi to south-east. 
It must also bo noted that the Shiant Islands, situated midway 
in the passage of the Minch, occupy a very crucial position for the 
determination of the problem, so far as the Avest side of the country 
is concerned. If foreign rock fragments arc found upon these 
islands, they must lie upon its 'western shores, and be of the rocks 
of the Long Island, if the ice came from the west ; — they must lie 
