204 Proceedings of the Royal Irish Academy. 



that action, combined with, the buoyancy given to the stones by the 

 growth of the seaAveed on them. Tidal currents of great depth, if 

 there is sufficient weed attached to a stone, woukl, although slowly, 

 yet gradually carry it into water of a sufficient depth to be influenced 

 by storm waves, after which the driftage would be accelerated. In 

 some cases I have observed that the buoyancy of the weeds attached 

 was superior to the weight of small stones, and that the latter, when 

 lifted from their sand bed, were at the mercy of the currents. Thus 

 any stone, no matter what its size, if the buoyancy of the weeds at- 

 tached exceeded its weight, may be drifted by a tidal current in any 

 direction, no matter what depth the water between the place from 

 which it first started to that at which it was finally stranded. In con- 

 nexion with the growth of seaweed, it may be mentioned that at the 

 Ballygeary pier, during the time the works were discontinued in 1877 

 till the resumption of operations in 1878, the divers found the foun- 

 dations (consisting of bags of concrete), laid down the previous year, 

 " overgrown by a thick forest of seaweed over eight feet in height." 



IV. — The Effects of the Travelling of the Beaclies on the Sarhours and 

 Piers letween Hooh Point and Dalhey Island. 



The principal piers and harbours on the coast line between Hook 

 Point and Dalkey Island are those at Kilmore, Ballygeary, Wexford, 

 Pouldufi (Cahore), Courtown, Arklow, Wicklow, Greystones, and Bray. 

 All of these, except those at Wicklow and Greystones, are unsatisfactory" 

 on account of the driftage of the beaches, in addition to which there is 

 at Courtown and Arklow the land sand driftage. The present state 

 of these different harbours and piers seems due to there having been 

 no allowance made for the travelling and the stoppage thereat of the 

 beaches under the influence of the tidal currents and wind waves. 

 Their condition suggests that in all such constructions, if it is possible 

 to avoid it, no impediments should be placed in the line in which the 

 beach naturally travels ; also that the piers ought to be perpendicular 

 to the coast line, and not curved ; as those of the first class act similar^ 

 to the headlands, and generate a "half counter-tide" a few hours be- 

 fore high water, which keeps sand from accumulating alongside them. 



KiLJiOEE Quay. — This is situated on the South Wexford coast, 

 about half way between St. Patrick's Bridge and Crossfarnoge Point 

 (Fig. 1, PI. 6). The harbour is sheltered by the pier from the W. and 

 S. W. winds, but it is open to S. E. and E. winds, and when these 

 blow strongly the fishing boats have to be drawn into the " old boat 

 harbour." The "flow-tide" di'iftage goes N. E. from the Saltees to 

 the St. Patrick's Bridge, and from thence westward to Crossfarnoge; 

 and, being stopped by the pier, it is rapidly silting up the harbour. The 

 driftage of the beaches and the direction of the more prevalent and 

 destructive winds being as described above, it would appear that the 

 most advantageous situation for the quay would have been on St. 

 Patrick's Bridge ; while to protect the harbour from the S. and S. W. 



