EVIDENCES OF THE AGE OF ICE. 
109 
by Davis Straits to the south with almost equal velocity. This 
current flows inshore on the North American seaboard, and also 
beneath the Gulf-Stream, but does not mingle with its waters. 
The Gulf-Stream is, of course, only one of many oceanic 
currents, but to us it has a pre-eminent degree of interest. It 
brings us genial showers, borne by the south-westerly winds, 
from the surface of its warm and steaming waters. It carries 
the temperature of summer even in the depths of winter as far 
north as the Great Banks of Newfoundland, and there main- 
tains it in the midst of the severest frosts. It is the presence 
of this warm water and a cold atmosphere in juxtaposition 
which gives rise to the u silver-fogs ” of Newfoundland, one of 
the most beautiful phenomena to be seen anywhere in the 
domains of the Frost King. Every west wind that blows 
crosses this stream on its way to Europe, and carries with it a 
portion of this heat to temper the inclemency of the northern 
winter. It is the influence of this stream upon the climate 
that makes Erin the “ Emerald Isle,” that clothes the 
shores of Albion in evergreen robes, and encourages the myrtle 
and magnolia to flourish at Mount Edgcombe in the open air 
all the year ; it carries West Indian seeds to the Scottish 
isles, wafts the floating pteropod-shells to the latitude of Ice- 
land, and renders the fauna of Spitzbergen richer than that of 
any other Arctic realm. 
But all earthly advantages are transient, and not even the 
Gulf-Stream can be expected to be always so partial to us as it 
is to-day. Indeed, geologists are aware that formerly, owing 
to the subsidence of that narrow belt of land, the Isthmus of 
Panama, at one time, and probably by the subsidence of the 
Mississippi Valley at another, the Gulf-Stream has more than 
once been diverted from our coasts, and our islands were, as far 
ns they were above water, glaciated even as the coasts of Labra- 
dor are at the present day. 
Let us briefly consider the evidences on which geologists 
have relied in writing this latest chapter in the geological his- 
tory of our island. These evidences are most abundant and 
varied ; some of them, indeed, lie close to our own doors, and 
may easily be studied and examined. I allude to the great 
series of deposits known to geologists as 66 glacial deposits,” and 
which have resulted either from the action of glaciers or ice- 
bergs, or some modification of them. These may be classified 
as follows : — 
I. — 1. Roches moutonnees. 
2. Striated rock-surfaces. 
3. Boulder-clay and ‘till.’ 
4. Moraines of valley glaciers. 
II. — 5. Erratic blocks. 
6. ‘ Karnes/ 1 eskers/ and sandy 
gravelly drift. 
7. Stratified clays with arctic 
shells. 
