Influence of Winds on the Gulf Stream. 163 



produced in the position of this line at the surface. The winds 

 sway the surface of these currents one way or another, some- 

 times for many miles, and they may retard or reinforce th ecur 

 rents in their flow. 



The winds which blow over this portion of the northern Atlantic 

 may for convenience be grouped in two classes. One may be 

 said to blow in a southeasterly direction and the other in a north- 

 westerly direction. The general tendency of the first group, or 

 the summer set, will be to drive the warmer waters at the sur- 

 face over toward the coast, thus forcing them above the colder 

 waters of the Labrador current. The other, or winter set, may 

 be considered to have the opposite effect on these waters, and 

 the final position reached after a cycle is completed will depend 

 on the relative velocities of the winds. It is not denied that 

 there are other factors which enter into this result, nor that this 

 position is not affected by the physical characters of the waters, 

 viz, their relative temperatures, densities, etc ; but it is claimed 

 that, after due allowance for other factors, the winds are the 

 most active causes of the daily and seasonal variations which 

 take place in this boundary. 



While these motion^p may equalize one another and the re- 

 sultant position remain the same from year to year, it is sup- 

 posable that there may be an excess in one of these directions 

 for a series of years, with the result that the boundary will be 

 carried far inshore from its normal position and thus to a great 

 extent obliterate the surface indications of the other current near 

 the surface. 



//. Lower Portion. 



Here only the general causes which produce and modify the 

 currents in the oceans can produce any change, unless by the 

 cumulative effect, spoken of in the previous section, modifica- 

 tions are brought about. As a rule, however, the variations 

 referred to might almost be classed as accidental, because they 

 are rarely productive of changes below 25 fathoms. When these 

 changes are brought about, they are usuallj^ of such a character 

 as to evade detection unless the averages of many observations 

 are carefully studied, when the change in the position of the re- 

 sultant can be seen. 



