172 SCARBA. GENERAL DESCRIPTION. 



throughout the narrow passage so much frequented by 

 ships, which lies between Jura and Scarba, and the main- 

 land. They arise from the constraint which the tide- 

 wave undergoes in a narrow and rocky channel, and are 

 displayed in a succession of currents and eddies that 

 render the steerage of a vessel exceedingly difficult in 

 calms, and produce, in gales of wind, a short and dan- 

 gerous breaking sea. The flood tide runs through the 

 gulf of Scarba from the eastward, being a branch of 

 the great stream which is here directed to the north ; 

 and as it is much obstructed in the passage of the 

 Coryvrechan, its rapidity is very considerable. This has 

 been computed at twelve miles or more in an hour; an 

 estimate which is evidently extravagant, and perhaps 

 nearly double the actual velocity. The ebb has of course 

 the reverse direction ; but the stream is less swift, and the 

 agitation of the water is consequently much less violent 

 and dangerous. This agitation is chiefly produced by 

 a rock of a pyramidal form, rising with a steep activity 

 from the bottom, which is here about 600 feet deep, 

 to within about ninety feet of the surface, and diverting 

 the course of the rapid tide already described. The 

 stream being thus obstructed, assumes numerous intri- 

 cate directions, which, interfering with each other, cause 

 the water to break with considerable violence. If there 

 be a fresh breeze, and more particularly if the motion 

 of the wind is opposed to that of the sea, this agitation 

 is increased to a frightful degree ; frightful at least to a 

 seaman who knows its dangers, although, to a landsman, 

 it may seem less terrible than the long surging roll of 

 the Atlantic wave. It is this breaking sea which con- 

 stitutes the real danger of the Coryvrechan, as, when 

 considerable, it will in an instant sink a vessel, unless 

 every thing is made secure on deck. The impulse of 

 the stream against the rock above described, produces 

 also a long and rapid counter-current or eddy on 

 the side of Scarba; which, returning into the principal 



