EVIDENCES OF THE AGE OF ICE. 
107 
Thus in the southern hemisphere, where the continents are 
diminished gradually towards the south, and where the moderat- 
ing influence of the ocean tends to eliminate all climatic differ- 
ences, the lines of equal annual temperature seem to be pretty 
regular, and in the Antarctic Ocean they may be considered 
parallel to the degrees of latitude. The most marked curves 
of these southern isothermals are developed immediately to the 
west of Africa and the west of South America, where the in- 
fluence of the currents of cold water flowing towards the equator 
from the Antarctic Ocean is most visibly demonstrable. 
In the northern hemisphere the sinuosities of the isothermal 
lines are much more marked than in the southern, and cut 
the degrees of latitude at all angles. One of the highest of 
these isothermal waves is that which rises in latitude 45° N., 
off the coast of Halifax, Nova Scotia, passes to the south of 
Newfoundland, ascends in a north-easterly direction past the 
south-east coast of Iceland* attaining its summit about latitude 
65° N. ; it then bends down to Drontheim, Stockholm, and 
Moscow, falling again nearly to latitude 45° N. in Central Asia. 
But whatever may be the sinuosities of the lines of equal 
temperature, they all indicate a more or less rapid decrease of 
heat between the equator and the two polar zones. 
In the interior of continents, the chief modifications of cli- 
mate are produced by mountain ranges and winds ; on coasts 
and islands the climate depends on ocean currents and winds. 
Happily for England, we enjoy here what is called an 66 insular 
climate.” There are special reasons why the climate of the 
British Isles is so much milder than that of any other place in 
the same latitude, and we may with advantage consider these 
exceptional circumstances before proceeding further. Take, for 
example, two parallels of latitude at the present day. Off Little 
Belle Isle, in the month of July 1864, Mr. J. F. Campbell * 
records the temperature of the air at 48°, water 40° (wind south 
when the temperature was taken), and icebergs in sight. Mr. 
Campbell passed bergs 400 ft. deep and 200 ft. long, and many 
others of far larger size, some being 150 ft. above the water. 
Belle Isle is in the same latitude as London. 
In 1831, Mr. Bedfield states that the harbour of St. John’s, 
Newfoundland, was completely blocked by ice so late as the 
month of June. This is 2° further south than the port of 
Liverpool, and yet one never heard of the port of Liverpool 
being blocked by ice, even in January ! Again, the limit of 
constantly frozen ground which extends to the southern border 
of Hudson’s Bay (where ice is found in digging wells in summer, 
at a depth of 4 ft. below the surface) is in the same latitude 
* In his “ Short American Tramp,” p. 66. 
