MR. T. HEELIS ON OCEAN SWELL. 283 



The S.E. Trade was fallen in with by this ship, on this 

 passage, on the 15th March, in latitude 28° 22' S._, longi- 

 tude 81° 13' E. 



The above are very remarkable observations. The ten- 

 dency of the wind, and the ordinary drift of the surface- 

 water, would conspire to place the ship ahead of her reckon- 

 ing instead of astern of it ; while the regularity in speed 

 of the current observed is a strong argument in favour 

 of their correctness. 



It should also be noticed that the swell caused by pre- 

 vailing winds often rolls home on a coast to which such 

 winds do not extend. The most familiar instance of this 

 is aflPorded by the westerly swell which is prevalent upon 

 the coast of Portugal, although the westerly winds which 

 cause it are separated from the coast by a tract occupied 

 by winds which blow parallel to the coast and are called 

 by sailors the Portuguese Trades. This peculiarity is well 

 worthy of the attention of the student of physical geo- 

 graphy, as having an important bearing upon the con- 

 sideration of the abrasion of coasts. 



From what has been above stated, I hope that it will 

 be seen that this subject, although not usually considered 

 worthy of attention and study, is of interest and import- 

 ance. To the scientific traveller it gives hints of agencies 

 being at work which, without it, would have been un- 

 suspected, and in districts little explored indicates either 

 the direction of prevailing winds or the set of currents ; 

 while to the seaman the cyclone swell gives timely notice 

 of impending danger, and of the position of his enemy. 

 Each of the classes of swell here mentioned has its own 

 peculiar character and appearance, not easily explained in 

 words, but from which an experienced eye can almost at 

 once detect its cause. 



