48-1 BEPOKT 1891. 



towards the west the shingle and sand from the mouth of the 

 Ehone, and from chffs of gravel abraded by the sea, and that 

 in its travel it forms spits across estuaries and bays, enclosing 

 them to form extensive lagoons, which are so marked a feature 

 of the coast near the mouth of the Ehone. 



Professor Aiisted, on the contrary, thinks storms bring sand 

 from the bottom of the sea, and in that way form these 

 singular lagoons. Vol. Ivii., page 365, says that observations 

 have shown that all along the coast of Portugal detritus is- 

 carried from north to south by the action of the sea, and, being 

 checked at the mouth of the rivers by the outcoming stream and. 

 south-west winds, it is first deposited on the north bank, then 

 drifted into the river, forming innumerable bars and shoals ; 

 but it is scoured out by floods, and drifted along clear of the 

 rivers. Vol. Iviii., page 272, notices the influence of the littoral 

 wave-currents at Genoa, which drift the sediment of the 

 River Bisagno tov^ards the port. Vol. Iviii., page 281 : Mr. 

 Kinahan, C.E., on the subject of the lagoons on the south coast 

 of Ireland, asserts that the tidal flow and its eddies carry the 

 beaches with them ; that ordinary wind-w'aves assist the tide- 

 currents when in the same direction ; that if these weaves 

 strike the beach at right angles they pile up the shingle, and 

 form what are called " full beaches "—if the waves are against 

 the tide-currents they cut out the beach, churn it, and draw 

 the shingle into deep water ; that heavy winds with the tide- 

 currents completely sweep the windw^ard portion of the beaches, 

 and fill up the leeward portion ; that ground-sw^ells strike the 

 beaches at right angles, and draw the shingle into deep water. 

 He notices the singular fact that stones of 2cwt.and 3cwt. 

 travel in water of 15 to 20 fathoms, greatly helped by the 

 floatage of great masses of seaweed that lift them along with 

 the slight impulse of each wave. 



Professor Ansted's opinion that sand is brought by storms 

 from the bottom of the sea has also been supported by others 

 in discussions on the bars of rivers ; but, besides being im- 

 probable, it is chsproved by the fact that the sea-bottom a few 

 miles from shore is covered by mud, not sand, and I think it 

 cannot be disputed that all sand of the seashore comes from 

 the land. 



There are innumerable instances of lagoons enclosed by 

 spits of shingle in this Island, some of which are on a very 

 large scale, and they all show unmistakable evidence of the 

 effect of waves and currents in conveying the material of the 

 beaches. 



Whatever part the tidal currents may take in transporting 

 the material of beaches, I think it is greatly exceeded by the 

 shore- or wave-currents, caused by the directions in which the 

 waves strike the beach; and, as far as I have observed, the 



