Reviews — Movements of Beach Sand and Shingle. 45 



the channel was deepened so as to give a minimum depth of 30 feet 

 at low- water over a width of 1000 feet, and a year afterwards it was 

 reported that no shoaling had taken place. Again, the sand-bar 

 which lies at the junction of the Mersey with Liverpool Bay has 

 been deepened by the use of suction-dredgers, and the channel so 

 excavated has not only maintained its depth during the severe tests 

 of the gales of two winters, but shows a tendency rather towards 

 deepening than shoaling. Other instances are given. 



The author believes that the mass of beach sand and shingle 

 which travels along the coast is due entirely to the erosion of the 

 cliffs (which may, of course, consist of hard rock or of ready-made 

 sand and shingle), and is not derived from the sea-bed. Hence 

 he is of opinion that the quantity of drift is limited, and that it 

 may be entirely stopped or its movement controlled, He, how- 

 ever, thinks that vast deposits of sand and shingle in bays and 

 sheltered places on the coast are due to causes which occurred in 

 remote ages, and which are no longer in operation — we presume 

 at the localities in question. Thus, in Morecambe Bay the sand- 

 beds cover an area of 90,000 acres dry at low-water, and in the 

 Duddon estuary they cover 9,000 acres. The Wash covers an area 

 of about 157,600 acres, of which about 84,000 acres consist of sand- 

 bods dry at low-water. It is quite true that rivers add very little 

 to these accumulations, but the waste of the coast now or formerly 

 bounded by cliffs composed of Drift sands and other deposits has 

 no doubt led largely to these great marine deposits. 



We would point out that salt-marshes are not exactly due to the 

 drifting of alluvial matter along tidal coasts and to its settling in 

 sheltered places, but rather to ordinary alluvial deposits being 

 formed in a broad valley or estuary, bounded by higher ground that 

 has on one side been subsequently worn away by the sea. The salt- 

 marshes along the Norfolk coast were probably formed in this wa}^ 



On the whole, while agreeing that the main contentions of the 

 author are supported by fact, we believe that agents now at work 

 will account for all the phenomena without recourse to higher and 

 more frequent tides as suggested by him. 



Among the matters discussed by Mr. Wheeler, we may mention 

 his conclusion that while wind and waves are the agents which 

 operate in eroding the cliffs and producing the sand and shingle, 

 the regular and continuous travel of the material along the coast is 

 due to the wave-action of the flood-tide. 



In conection with these views, we may refer to those of Mr. F. P. 

 Gulliver, given in an article on " Cuspate Forelands," ^ or headlands 

 formed by beach shingle and sand, and also as delta deposits. He 

 points out that when the supply of waste from the cliffs has in- 

 creased bej^ond the power of the currents to immediately deposit 

 it offshore, then transportation takes place alongshore, and the 

 growth of forelands may take place by tidal- and ocean-current 

 action. Ocean currents have but little effect on the inner shore-line, 

 or that of the more protected coasts of bays, sounds, etc. ; there 

 1 Bull. Soc. Geol. America, toI. yH, 1896. 



