16 Fishery Board for Scotland. 



the eastern shores of the United States ; it is that " great river in the 

 ocean," which is called the Gulf Stream. This narrow river^like Gulf 

 Stream gradually loses its heat, its speed, and its river-like form, and 

 at the same time it is deflected westward, partly by the direction of 

 the American coast, partly by the influence of the earth's rotation 

 upon its northward velocity. It is presently caught up by the strong 

 westerly winds which are characteristic of the north temperate 

 Atlantic, and by all these influences combined (and especially the 

 last), it is merged in that great east-going drift which is still often 

 called the " Gulf Stream," but which it were better to call the North 

 Atlantic Current. It is this great easterly current which warms our 

 own western shores, ameliorates the climate of the whole coast of 

 Norway, tempers that of distant Spitzbergen, and sends its offshoots 

 not only into the North Sea, but also to both sides of Iceland, to the 

 east coast of Greenland, and even dips round Cape Farewell into 

 Davis Straits. On the other hand, another portion of the same great 

 Atlantic drift eddies southwards, by Spain and the Moroccan coast, 

 by the Cape Verdes towards the Equator, to resume its circuit west- 

 ward in the Equatorial Current. 



Within this vast swirl of waters, between the westerly drift of 

 the Equatorial Current to the southward, and the easterly drift of 

 the " Gulf Stream " or Atlantic Current far to the north, lie the almost 

 motionless waters of the Sargasso Sea. 



The cold currents from the pole run southward, in great part, as 

 we have already said, below tlie surface, and even at the bottom of 

 the ocean ; this being due to the greater density of their cold waters, 

 which are compelled to sink beneath the warm. But at the same 

 time, much of the very cold water from the far north is largely mixed 

 witli fresh water from the Arctic ice and snow : and this admixture 

 of fresh water may render the mixture lighter, in spite of its coldness, 

 than the warm but salt waters of the ocean. Accordingly, we have 

 not only the cold returning bottom currents to think of, but we have 

 also certain cold, south-going surface currents, and the greatest of 

 these is that which coasts down the east side of Greenland, close to 

 the shore, joins with a still larger bulk of water from Davis Straits 

 and Baffin's Bay, and again with more cool water from Newfoundland 

 and Labrador, and then (deflected westward by the rotation of the 

 earth) hugs the coast of the United States, between the Gulf Stream 

 and the shore. 



We are now at length in a position to consider the Mean Surface 

 Temperatures of the North Atlantic, and to understand them in 

 relation to the system of currents which we have so briefly described. 



On the southern border of our chart (Fig. 1), where it com- 

 mences in about lat. 30° N,, we see that the mean annual temperature 

 is about 22° C, but that, as we pass westward from the African 

 coast towards Florida, the temperature gradually increases from 

 about 20° to somewhat over 23*^. This gradual increase is the direct 

 result of the great North Equatorial Current ; for, evidently, at the 

 eastern end of our line, we have cooler waters which have come down 

 in the great eddy from the north (constituting the so-called Canary 

 Current) : on the western side, between about 50"^ and 70° W., we 

 have the almost motionless waters of the Sargasso Sea, heated by 



