The Geographical Journal (Journal of the Royal Geographical Society): Volume XII, No. 2 [‎267v] (37/154)

128 THE ANNUAL RANGE OF TEMPERATURE IN THE SURFACE WATERS OF THE
January and July, published in the ‘ Challenger Report ’ by Dr. Buchan,
it will be seen that there is a general parallelism between the regions
marked off by the blue colours and the position of the anticyclomc areas
of the ocean. In these intermediate regions, between the equatorial band
and the two circumpolar bands of small range, there is probabl) at a
times of the year more insolation, or sunshine, and consequently a greater
absence of clouds, than is to be met with in the tropical or polar areas,
which may account to some extent for the wide range. It will be noticed
that the deepest shades of blue are situated on the polar sides of the
anticyclonic areas, and in these positions the greatest cyclonic dis
turbances are met with; in these regions the strength and direction of
the winds and currents vary at different times of the year, owing to the
position of the sun in the months of January and July. Cm rents from
widely separated sources are in this way frequently carried over the
same position even in the open ocean.
A large range of temperature, due to up welling, as a result of the
action of the winds, is indicated by the blue colours along the west coasts
of Africa and South America, and on the east coast of Africa, near Cape
Guardafui. The relatively wide range represented by the blue colour
which extends from the Gulf of Guinea to the westwards about the
equator, and a similar arrangement at the equator off the Gulf of
Panama, seem to be due to currents variable in speed but constant in
direction, producing greater upwelling at one season than at another,
but in currents which are relatively constant in direction and speed
a small range of temperature usually occurs.
It is to be noted that in the tropical regions the lines showing the
variation spread outwards in the shape of a fan towards the eastern
shores of the continents, whereas, on the other hand, in the northern
and southern temperate regions they show a tendency to spread out in
like manner towards the western shores of the continents ; this is espe
cially the case in the Atlantic. This position of the lines is what
would be expected from a consideration of the general system of winds
and oceanic circulation.
5. Relation of Range of Temperature to Biological Phenomena.
Where cold and warm currents meet at the surface of the ocean
there is a rise of temperature for the animals of the cold current, and a
fall of temperature for the animals of the warm current, which results
in a plentiful destruction of organisms. The tow-net collections during
the Challenger expedition gave frequent illustrations of this fact by the
dead animals collected in such positions off the coast of North America,
off the Cape of Good Hope, in the North Pacific, and elsewhere.
Dr. 0. Fischer records a remarkably large number of bacteria on the
borders of such meeting currents. This destruction of life is not
limited to minute pelagic organisms, but occasionally affects animals