46 National Geographic Magazine. 



figures for mean velocity and temperature from surface to bottom 

 ai'e, it will be noticed, far below those for the surface current 

 alone, where the velocity is often as great as five knots an hour, 

 and the temperature as high as 80°. The indicated horse-power of 

 a great ocean steamship — " La Bourgogne," " Werra," "^Umbria " 

 and " City of New York," for example — is from 9,000 to 16,000 ; 

 that of some modern vessels of war is still greater ; the " Vulcan," 

 now building for the British Government, is 20,000, and the 

 " Sardegna," for the Italian Government, 22,800. Again, if we 

 convert into its equivalent horse-power the potential energy of 

 the 270,000 cubic feet of water per second that rush down the 

 rapids of Niagara and make their headlong plunge of 160 feet 

 over the American and Horse-shoe falls, we get the enormous 

 sum of 5,847,000. The Gulf Stream, however, is every hour 

 carrying north through the straits of Florida fourteen and three- 

 tenths cubic miles of water (more than three thousand times the 

 the volume of Niagara), equivalent, considering the amount of 

 heat it contains from 71° to 32° F., to three trillion and sixty 

 three hillion horse-power, or more than five hundred thousand 

 times as much as all of these combined ; indeed, considering only 

 the amount of heat from 71° to 50°, it is still two hundred and 

 seventy-five thousand times as great. 



Sweeping northward toward Hatteras with its widening torrent, 

 its volume still further increased by new supplies drawn in from 

 the Bahamas and the northern coast of Cuba, its color a liquid 

 ultramarine like the dark blue of the Mediterranean, or of some 

 deep mountain lake, it then spreads northeastward toward the 

 Grand banks of Newfoundland, and with decreasing velocity and 

 lower temperature gradually merges into the general easterly 

 drift that sets toward the shores of Europe about the 40th parallel. 



The cold inshore current must also be considered, because it is 

 to great contrasts of temperature that the violence of storms is 

 very largely due. East of Newfoundland the Labrador current 

 flows southward, and during the spring and summer months 

 carries gigantic icebergs and masses of field-ice into the tracks of 

 transatlantic steamships. Upon meeting the Gulf Stream, a 

 portion of this cold current underruns it, and continues on its 

 course at the bottom of the sea ; another portion is deflected to 

 the southwest, and flows, counter to the Gulf Stream, along the 

 coast as far south as Hatteras. 



The broad features of these great ocean currents have thus 



