Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/63

Rh AND CA.HORE SHINGLE EE.YCI1, CO. WEXFORD. 37 there are " countertides " in dif- ferent places, the principal one being off Beer Head, where the tide revolves, the " flow " tide at the same time running both to the N.E. and to the V., while there is a " drain" to the 8.S.W. From the soundings on the Ad- miralty Charts very little can bo learned concerning the travelling of fragments in deep water : one fragment on every square foot of the bottom of the bay would pass unnoticed, while one fragment on every square yard would be more than sufficient to supply the ma- terials to keep up the Chesil beach. 9. Portland Bill, the headland that bounds Lyme Bay on the east, is the headland, down stream (in regard to the " flow " tide), nearest to Swanage, the English end of the nodal or hinge-line of the tide in the En- glish Channel. 10. At Portland Bill it is high water (at full and change of moon) at 7 o'clock. 11. At Swanage is the least "rise" of tide and the greatest current in the English Channel. The range is 5 feet. 12. The current in the English Channel from its Atlantic en- trance (a line from the Scilly Islands to Ushant Isle)* increases the beach to theS.W. and on the back (south) of the Dogger bank (the shoal off the mouth of the lagoon called Wexford Harbour). From the Dogger bank this shingle drifts N.E. into deep water, from which some pebbles are cast up on the Black water bank, along which they seem to travel, some to be driven in shore on the Cahore beach, while many of them go northward past Cahore Point, where they are found on the different beaches. North of the Dogger bank, between it and the Cahore beach, the rock-fragments that fall from the drift-cliffs (which in places are composed of very stony ma- terial) are sucked seawards by the back wash, and few or none travel along the beach : neither are there any pieces of the Gree- nore rocks to be found here- abouts. 9. Cahore Point, which bounds Wexford Bay on the north, is the headland, down stream (in regard to the "flow" tide), near- est to Courtown — the Irish end of the nodal or hinge-line of the tide in the Irish Sea. 10. At Cahore Point it is high water (at full and change of moon) at 7 o'clock. 11. At Courtown is the least " rise " of tide and the greatest current in the south portion of the Irish Sea. The range is 2 feet. 12. The current in the Irish Sea from its Atlantic entrance (a line from Cape Clear to the Scilly Islands) * increases till it entrance, on account of the tide in places running more swiftly round head- lands, also on- : account of the complications of tides due to the respective offset bays— that of the Gulf of St. Malo off the English Channel, and that of the Bristol Channel off the Irish Sea.
 * In both cases the currents do not increase in regular progression from the