Supplement to ''Nature" April 24, 1902. 



to its true cause, the gale, aided undoubtedly by the raised 

 water-level, due partly to the tide, and also partly to the 

 heaping up of the sea against a lee shore by an on- 

 shore gale ; whilst the wave-stroke at Peterhead was 

 not due, as implied above, to a tidal rise of 8 feet, 

 but, as mentioned a few pages earlier, to the depth 

 into which the breakwater has been carried, the great 

 exposure of the site, and the large waves, attaining 30 

 feet in height and 600 feet in length during storms, 

 which, consequently, come against the structure. 



Numerous instances have been frankly quoted in the 

 two chapters on wave action and littoral drift of the 

 effect of waves in storms in transporting material along 

 the coast, reference to two of which must suffice ; — 



" In the Solent, near Hurst Castle, a shingle bank, 2 

 miles long and 12 feet high, consisting principally of 

 flints resting on a clay base, was moved forward in a 

 north-easterly direction forty yards during a storm in 

 I1S24. . . . During a licavy gale stones weighing from 2 

 to 3 cwt., with large masses of seaweed growing on 

 thtm, were loosened from their bed at a depth of fifteen 

 fathoms, and tlirown on to the beach." 



Compared with the forces displayed by these effects, 

 and the others given in the book produced by waves in 

 storms, the wavelets of the flood tide sink into insig- 

 nificance ; and, thanks to the fairness with which these 

 examples have been given, it may be anticipated that 

 an unbiassed, intelligent perusal of these two chapters 

 will lead to conclusions at variance with those of the 

 author, and that it will be realised that waves in storms 

 are the chief forces producing changes in coasts and 

 littoral drift, exercising their maximum effect during 

 high water of spring tides, and when acting in unison 

 with the tidal currents. 



From an engineering point of view, the most interest- 

 ing part of the book is comprised in the three chapters 

 on coast protection by sea-walls and groynes. Sea-walls 

 formed of embankments with pitched slopes, or more or 

 less upright masonry or concrete walls, serve for directly 

 warding off the attacks of the waves in storms from the 

 shore, cliffs, or sea-drives and promenades ; whilst groynes 

 of timber, fascines, or concrete are projected at intervals 

 down the beach to arrest the littoral drift, and by thus 

 gradually raising the strand prevent the sea from eroding 

 the shore. Unfortunately groynes, by collecting the 

 drift along one part of the beach, deprive the unprotected 

 portion further leeward of the supply by which its losses 

 by erosion would be naturally replenished ; and, con- 

 sequently, the advance of a length of foreshore produced 

 by groynes is accompanied by a retrogression of the 

 adjacent portion from the cutting off of the drift. A 

 pitched slope is adopted where the shore to be protected 

 is low and sandy, and where materials for a wall are 

 deficient, as along the coasts of Holland and lielgium ; 

 and a wall is resorted to where cliffs line the coast, or a 

 sea-drive is constructed considerably above the beach ; 

 and this variety in construction is due to differences in, 

 the conditions rather than, as suggested by the author 

 to differences of opinion amongst engineers. A simple 

 upright wall has advantages for breakwaters over other 

 f.irms where the bottom is rocky and the depth moderate ; 

 but in contrasting Dover pier, which has not be( n free 

 from injury, with the breakwaters at Cherbourg, Plymouth, 

 NO. 1695, VOL. 65] 



and Alderney, the author has fallen into a very common 

 error of overlooking the differences of e.xposure and 

 depth of water at these sites ; for Dover is situated in 

 one of the most sheltered places of the English Channel, 

 whereas Cherbourg is much more exposed, and the 

 breakwaters of Plymouth and .\lderney are open to the 

 .\tlanlic, and the latter extends into a depth of 130 feet 

 at low water. Sea-walls, however, differ very materially 

 from breakwaters in being built near high-water mark, 

 and therefore upright sea-walls are subject to consider- 

 able erosion at their toe, from the recoil of the waves 

 dashing against them, which affects even chalk and shalei 

 so that unless the foreshore consists of firm rock, the 

 sea-wall, which is usually curved or battered on the face, 

 has to be founded below the limit of erosion, or more 

 commonly is provided with an apron to protect the por- 

 tion of the beach near the sea-wall from the breaking 

 and recoiling waves. A stepped face is sometimes given 

 to sea-walls, so as to impede the upward run of the 

 waves and break up the recoil ; but the work must be 

 solidly built, and only a moderate width given to the 

 steps, otherwise the reduction of the weight on the face 

 blocks due to their projection might lead to their dis- 

 location under the impact of the waves. The author 

 regards a sea-wall curving on its face from the apron 

 laid at the slope of the beach, to the vertical at the top, 

 as the best form, and no doubt such a form leads the 

 waves from a horizontal to a vertical course with the 

 least practicable opposition ; but at the same time, by 

 minimising the impediments, it causes the waves to rise 

 higher above the wall, and the upper portion of the water is 

 driven over the promenade by the gale. In the chapter on 

 " Examples of Sea-walls," several sections of sea-walls 

 are given ; and both this and the succeeding chapter on 

 " Groynes " contain many interesting details of these 

 works ; and the book as a whole furnishes a considerable 

 amount of inforination about the coasts of England, 

 which must have involved much time and trouble to 

 collect. 



EVOLUTION AND ANTI-MATERIALISM. 

 Piiiiiiplfs of Western Civilisalion. By Benjamin Kidd. 

 Pp. vi-f5i8. (London: Macmillan and Co, Ltd., 

 1902.) Price 15^'. net. 



TO those who, some years back, read Mr. Benjamin 

 Kidd's '' Social Evolution " with great interest and 

 learnt much from it, his new book will be a profound 

 disappointment. Undertaking to settle all the great 

 questions with which our civilisation is confronted, it 

 leaves many important facts out of sight and fails to find 

 a remedy for the main evils. The style is ponderous and 

 difficult. In some parts \ery careful reading is required 

 if the exact meaning is to be made out. 



The line of argument followed is this. Evolution has 

 upset all our old philosophies and obliged us to remodel 

 our way of thinking. Since Darwin's time, evolution has 

 undergone a great development in the hands of Weis- 

 mann. We now see that the future is predominant over 

 the present. The overwhelming proportion of individuals 

 interested in the struggle for existence are yet unborn. 

 The contending races are struggling for " an advantage, 

 probably always far in the future, to which the individual 



