Between Florida and the shoal waters on the Bahama Banks the Gulf Stream is about 50 miles wide, approximately 350 fathoms deep, and flows northward at the rate of from four to five miles an hour. Its temperature is about 80 deg. F. It is estimated that this great river in the ocean carries 90,000,000,000 tons of water per hour past a given cross-section. Its course is northward along the immediate border of the continental shelf until it arrives opposite the Carolina coast, and thence northeastward, thus giving it a constantly increasing distance from the land. To the north of the Bahamas it receives as a tributary the portion of the equatorial current, perhaps even greater in volume than the true Gulf Stream, which is deflected northward by the West India Islands and their associated banks. Continuing its course, it is deflected still more towards the northeast owing to the influence of the earth's rotation, at the same time expanding and losing velocity so as to become a surface drift rather than a well-defined current. Under the influence of the prevailing westerly winds of the north Atlantic, the waters delivered by the Gulf Stream pass the vicinity of the British Islands and in part enter the Greenland Sea. [Illustration: PLATE I.--Orographical features.] The transfer of the vast amount of warm water carried by the Gulf Stream far to the north is counterbalanced in part by a southward-flowing cold current which emerges from Davis Strait, and being joined by another cold current from the eastward of Greenland, continues southward under the name of the Labrador current, past Newfoundland and Nova Scotia to the Massachusetts coast, and is thought to exert an influence on the temperature of the sea even as far south as Cape Hatteras. While the Gulf Stream in the northern portion of its course curves eastward and departs from the American coast, the southward-flowing Labrador current is turned westward and follows close along the border of the land, and mainly over the continental shelf. The chief effect of the cold current from the north in proximity to the coast of the continent is to bring to the adjacent land a lower mean annual temperature and especially colder and more stormy winters than it would otherwise experience. This tendency is augmented by the icebergs carried southward with the Labrador current. In a similar way, the northward-flowing warm current gives Florida and the Carolinas a subtropical climate, admits of the growth of reef-building corals about the Bermuda Islands, and carries so much warmth to northwestern Europe that its climate is milder and more humid than one would expect from its geographical position.