to tidal streams, the velocity of which depend^ on time and position, 

 is given and some observational evidence supporting the theory is 

 analyzed. The author states that in deep vmter the average length 

 of waves appear to expand or contract at the same rate as the 

 general surface of the water on which they are moving. He con- 

 cludes that; fluctuations in tidal cycles of the periods of record- 

 ed waves can be satisfactorily attrihited to the action of tidal 

 streams; and the change in period will be proportionately small 

 when the tidal streams are weak or where the waves complete their 

 passage through the tidal area in a small fraction of a tidal 

 cycle o 



"Model Experiments on the Belgian Ports of the North Sea," Lo Bonnet and 

 J. Lamoen, Dock and Harbour Authority, Volo XXX, Nog. 3-48-350, October- 

 November-December 19A-9o 



"Biis article is a detailed review of the book, "Etude des Ports 

 :telges de la Mer du Nord^" by Lo Bannet and Jo Lamoen^ It des- 

 crites model experiments for the Belgian ports of Zeebrugge and 

 Ostend separated by a distance of only twelve miles, but present- 

 ing two widely different problems. Zeebrugge is a single curved 

 mole enclosing a single area of the sea and encroaching upon the 

 natural flow of the coastal currents; Ostend is a canalized outlet 

 debouching on the sea Td.th no appreciable interference of the 

 littoral currents. At Zeebrugge the problem was to provide remedial 

 measures for the silting up the harbor, while at Ostend the pro- 

 blem was to investigate proposed entrance channel improvements. 

 The progressive series of experiments conducted in the harbor 

 models under various projected improvements are discussed and 

 illustrated in detail. Test results of the wave reduction with- 

 in the harbor modelled on the v^'rious projects are given. The 

 outstanding features of these model experiments are the practical 

 m.ethods adopted to achieve results related to the actual phenomena. 



58 



