156 



KNOWLEDGE 



[August 1, 1892. 



from the north Polar regions begins to be felt, and it is a 

 matter of considerable difficulty to assess the value of this 

 force, or to locate with any degree of accuracy the line 

 along which it is applied. The general direction of the 

 Labrador current and its ramifications was first discovered 

 by Cabot in 1-197, but although many attempts have been 

 made to give an exact position to the line of demarcation 

 between the waters of the Gulf Stream and those of the 

 icy current contiguous to it, our present knowledge of 

 the subject is yet far from being marked by scientific 

 precision. 



Navigators report that the Gulf Stream swirls by its 

 antagonistic neighbour with a clearly defined ripple, that 

 on leaving the former current for the latter the transition 

 is rendered perceptible to the sight by the water changing 

 from deep blue to light green, and to the sense of touch by 

 a very marked reduction in the temperature. Scientific 

 research, however, fails to establish the existence of such 

 well-marked boundaries, although the fact of Admiral 

 Milne, in the line of battle ship Xilf, finding a variation of 

 temperature of some 25° between the sea at his stern and 

 at his bow is indisputable. The most reliable index that 

 a vessel is in the vicinity of the meeting of the waters is 

 the partial condensation of the aqueous vapour, for the 

 convergence of two air columns of differing temperatures 

 and humidities often results in dense fogs. But even this 



hygrometrio evidence is not absolutely reliable as revealing 

 the exact locale of the dividing line. The variations of 

 the anti-trades are frequently the cause of the interposition 

 of a;r columns from the Gulf Stream between the atmos- 

 pheric masses superincumbent to the Labrador current. 

 The eastern side of Newfoundland has its mean annual 

 temperature raised considerably by its proximity to the 

 warm current, while Nova Scotia benefits in a lesser but 

 still marked degree. Halifax harbour is never blocked by 

 field ice, and the formation of sheet ice in the harbour 

 itself never obstructs the navigation of steamships. The 

 mean temperature for the month of May averages 41^ or 

 45° F. 



Somewhere between the latitude of Cape Cod and that 

 of Newfoundland, the Gulf current undergoes the process 

 of division. One section Hows to the north-east towards 

 Northern ?]urope, while the other pursues an easterly 

 direction, which gradually becomes south-east and then 

 almost due south. 



It will be readily seen that the difficulty of obtaining 

 accurate information relative to the direction and speed of 

 ocean currents is very great, and that it is only by many 

 observations extended over a number of years that 

 sufficient data can be procured to generalize from. The 

 Hydrographical Department of the United States has 

 conferred lasting benefits upon Atlantic na^•igators by 



Explanalion of sleich showinr/ tlie :Sorih Atlantic Sargasso.— 'i\\e arrows indii-ate tlie direction of the currents. 

 Tlie areas marked I, 2', 3, 4 show tlie accumulation of different 'quantities of Sargasso. Fig. 1 marks the area of greatest 

 density. The minimum of frequency is encountered in the zone numbered 4, while beyond that area weed accumulation 

 is hardly ever noticeable. The shaded coast-line signifies the presence of a weed there identical with the weeds occurrent 

 in the Sargasso Sea. In fact, the shaded coasts are the strips of littoral from which the Sargasso weed is detached. The 

 dotted ellipse signifies the areas of frequent calms. The shaded portion of the North Atlantic, marked A, B, C, marks the 

 limits of the Sargasso Sea as laid down by Humboldt. 



