There is, as we observed yesterday, a tongue of warm water in the Atlantic to the west of Ireland that extends north-eastwards up towards Scandinavia. The first scientific reference to the Gulf Stream, as in the case of so many other natural phenomena, is to be found in the writings of Benjamin Franklin in the late 18th century. Franklin had noticed that the mail packets from Falmouth to New York were generally a fortnight longer at sea than merchant ships plying from London to Rhode Island - a difference which neither distance nor variations in wind speed or direction could explain. He was not long in discovering the reason why; in 1769 he wrote to the Secretary of the British Post Office to tell him about "the Gulph Stream, a strong current which comes out of the Gulph of Florida, running at a rate of three or four miles an hour".
Explaining the anomalously time-consuming voyages, Franklin went on: "It is supposed that their fear of Cape Sable Shoals, George's Banks or Nantucket Shoals hath induced them to keep so far to the southward as unavoidably to engage in the same Gulph Stream which occasions the length of their voyage, since the current being 60 or 70 miles a day, is so much subtracted from the way they make through the water."
Very little more was learned about the current until it was charted more than a century later by the American oceanographer, Mathew Fontaine Maury. As we now know, it flows northwards along the east coast of the United States, and then, continuing as the North Atlantic Drift, it divides the ocean neatly into two as it flows across towards Europe in an east-north-easterly direction. Then, passing close to the south-west coast of Ireland, the North Atlantic Drift veers north-eastwards to continue along the eponymous coastline as the warm Norwegian Current.
Maury described the phenomenon in very lyrical terms: "There is a river in the ocean; in the severest drought it never fails and in the mightiest floods it never overflows; its banks and its bottom are of cold water, while its current is of warm; the Gulf of Mexico is its fountain, and its mouth is the Arctic Seas. It is the Gulf Stream; there is in the world no other such majestic flow of waters."
Modern oceanographers think of this great current as a boundary which prevents the warm waters of the Sargasso Sea from merging with the colder denser waters nearer shore. But they are unenthusiastic about the name, since very little of its water actually originates in the Gulf of Mexico.