On the Surface Temperature of North Sea and North Atlantic. 17 



long exposure to a semi-tropical sun : to the westward of the Sar- 

 gasso Sea. we have the hot north-going waters of the Antillean 

 Current, and finally, still nearer to the shore, the still hotter waters 

 of the Gulf Stream. For these latter phenomena, to the westward, 

 our own temperature data are very scanty, and the isotherms on the 

 map (westward of 70") are filled in approximately from Dr. Schott's 

 chart and other sources. 



The next important feature in the map, and the most striking of 

 all, is the band of close-packed isotherms running from_ about Cape 

 Hatteras, more or less parallel with the American coast, until it bends 

 more to the northward beyond Newfoundland ; here the close-packed 

 isotherms begin to spread apart, opening out like a fan, to cover the 

 whole region of the North Atlantic. This band of isotherms, or 

 region of rapid change of temperature, is evidently the simple and 

 natural result of the meeting of the warm waters of the Atlantic 

 with the cold waters brought down from the north by the Labrador 

 Current. The latter first drives a wedge into the warm ocean to the 

 east and south-east of Newfoundland ; and here, where the hot and 

 cold waters lie side by side, fog and rain and snow, according to 

 season, are the inevitable consequence. And all down the American 

 coast, as far at least as Cape Hatteras, the cold current hugging the 

 shore (under the influence of the earth's rotation), and the hot current 

 passing northward on its outer side, produce within a narrow belt a 

 succession of rapidly changing temperatures, which appear on our 

 chart as the band of close-packed isotherms. 



To the northward and eastward, in the middle and eastern 

 Atlantic, we see that the isotherms are all more and more curved or 

 bowed, with their convexities to the north, or rather to the north- 

 east ; and accordingly, along a line from Labrador towards the Irish 

 coast, we are passing steadily from colder to warmer waters. Along 

 this line, beginning at the west, we start from the cold Arctic waters 

 which have come down Davis Straits and out of Baffin's Bay ; and the 

 warmer waters which we gradually reach are those which have come 

 from the southward, out of the great Equatorial Current, partly by 

 way of the wind-swept North Atlantic Current of which we have 

 spoken, and partly as a consequence of the general tendency of the 

 warm and light ocean water to creep northwards, slewed as it is, at 

 the same time, eastward by the rotation of the earth. 



Off our own shores we see the Atlantic Current, or so-called 

 " Gulf Stream," carrying part of its warm waters into the narrow 

 seas, that is to say, into the Irish Sea, and through the English 

 Channel into the North Sea. Bends in the isotherms correspond 

 visibly with this phenomenon ; while the curved isotherms of the 

 ocean become still more curved to the northward of our islands, as 

 the great current passes on its way to the coasts of Norway and far 

 into the Arctic Sea, Eastward of Iceland these isotherms show a 

 subordinate bend in a southerly direction ; this is an indication 

 (which more detailed information would probably make much more 

 distinct) of a branch of the great cold water current coming south- 

 ward from the pole ; and indeed there is a series of gentle bends in 

 all the isotherms to the north of Scotland (with their concavities 

 to the north), indicating a slow southward drift of colder waters. 



Returning to the western coasts of the British Islands, and pass- 

 2 



