J. Crol—Cause of Mild Polar Climates. 145 
certainly may be regarded as proof that no real glacial epoch 
could have occurred during that period. But has it been satis- 
factorily ascertained that those beds are wholly devoid of such 
materials? Those beds, I presume, have been searched by 
geologists for their fossil contents rather than for stratigraph- 
ical evidence of glacial epochs. It is remarkable how long 
the evidence of glaciation sometimes remains unobserved when 
no special attention is devoted to the matter. As examples 
of this we know with certainty that the Orkney and Shetland 
Islands were during the Glacial epoch overridden by land-ice ; 
and yet geologists who had often visited these islands declared 
that they bore no marks of glaciation. So recently as 1875 the 
low grounds of Northern Germany were believed to be without 
glacial strize ; yet when German geologists began to turn their 
attention specially to the subject, they found not only evidence 
of glaciation, but indisputable proof that during the Glacial 
epoch the great Scandinavian ice-sheet had advanced over the 
Country no fewer than three separate times down to the lati- 
tude of Berlin. I have myself seen the striated summit of a 
Feasons why these markings so long escaped detection is doubt- 
less due to the fact that they were on a spot which no geolo- 
Search had been made for them or because they were under 
Conditions in which they were not expected to be found. It is 
and foreign material, indicating the existence of glacial condi- 
hons during that period. 
Considerable importance has been attached to the statement 
of Professor Nordenskjéld that he failed to observe in the 
Stratified deposits of Greenland and Spitgbergen any evidence 
Whatever of former glaciation in those regions. “ We have 
never seen,” says he, “in Spitzbergen nor in Greenland, in these 
Sections often many miles in length, and including one may 
