Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/65

Rh AND CAHOBE SHINGLE BEACH, CO. WEXEOKD. 39 Admiralty Chart would seem to that there are currents on either suggest that there is a current side of the long banks running hugging the west shore of Lyme direct from Greenore to Cahore. Bay from Start Point to Berry Head, and running from this part of the bay direct onto the Chesil beach. From a consideration of this comparison, it will be evident that there is a strikiug agreement in the circumstances of the beaches at Chesil and Cahore. The most distinctive differences are : — 1. The great length of the Chesil beach. 2. The regular gradation in the size of the pebbles forming this beach. 3. The great height to which the beach is piled up near its eastern termination. These peculiarities may be explained by the circumstances under which it was formed and is kept up. Chesil beach is open to the incoming tidal current and to winds which are not only the prevailing, but also the most effective winds, and which, at the same time, come in a direction similar to that of the incoming tidal current, and thereby considerably augment it. The Cahore beach is protected from the landward currents from the incoming tidal stream by the off- shore banks in Wexford Bay. The prevailing winds (S.W. winds) have no effect ; the more effective winds in regard to the driftage, come from the S.E. ; but the more prevailing winds that effect the driftage on the coast are from the N.E.; and these considerably change and modify the tidal driftage. Take, for instance, their effects on the mouth of Wexford Harbour. The tidal driftage tends to extend the Dogger bank towards the N.E. Continued winds from the north-east, however, will stop this driftage, and force the sand into the N.E. channel, and thus raise the " bar," so that at times it is scarcely passable*. These winds, while they last, have considerable effect on the Cahore beach, pushing it towards the S.S.W., and modifying the arrangement of the fragments so that the pebbles in it are arranged more like those in the Chesil beach after continued winds from the S.E., than at any other time. The off-shore banks in Wexford Bay are probably due, in part, to the frail nature of the shore-cliffs t ; it is likely, however, that they may be due in part to the circumstance of the wind-waves rarely con- spiring with the tidal current, which consequently seldom acts to the most advantage. The efflux out of Wexford Harbour also has a considerable effect on the banks ; the Lucifer bank, since the intaking of a considerable portion of the tidal muds of the lagoon, is gradually being carried away, as is apparent on a com- parison of the chart of 1847 with that of 1873. These banks, regular traders from the port can scarcely get in or out. t Land-wind driftage must also considerably augment them, as during the continued winds from the north-eastward clouds of sand are carried for miles southward, along the coast-line into Wexford Bay ; part to be lodged by the water on the banks, and part to be carried again northward by the tidal stream.
 * Wexford Bay during this winter, 1875-76, has been so silted up that the