Reviews — A. R. Hunt — Ripple-marks and Wares. 521 



ripples with unequal sides. Ripple-marks on shore are better 

 preserved in pools, where they are more or less protected from 

 continuous currents. The direction of Ripple-marks has, however, 

 no necessary relation to the direction of the wind. 



The bottom of Torbay, usually smooth, was found to be strongly 

 rippled by swells following a gale, and the author has discussed 

 at some length the depth to which submarine deposits may be 

 disturbed. Evidence is brought forward, from the occurrence of 

 rolled shells, of disturbance of the bed of the sea at depths up to 

 about 38 fathoms ; and even at 40 or 50 fathoms, though the Wave- 

 action may be slight, it is not to be disregarded, at any rate in an 

 area subject to oceanic swells and where there is a tidal current. 

 The evidence obtained from a soda-water bottle dredged up from 

 40 fathoms, showed that the sea-bottom was subject to alternate 

 periods of rest and disturbance. This bottle was found to contain 

 55 species of shells, which must have been washed in by wave- 

 currents during heavy storms. Serpulce were growing in the neck 

 of the bottle, and they prevented two of the shells (Pecten opercu- 

 laris and Fusus gracilis) from being extracted. 1 



Disturbance in shallower water at depths of six fathoms in 

 Torbay is shown by the occurrence on the shore of two species of 

 Cardium (G. acitleatum and G. tuberculatum). Specimens of the 

 former, which were much rolled, had been derived from the sea-bed 

 beyond the six-fathom line where they are known to flourish. 

 Thus different species of Mollusca come to be grouped sometimes 

 separately, sometimes together in deposits of the same age ; while 

 by the changes in the supply of mud or sand species locally become 

 extinct, and may be replaced by another species. 2 



Storm waves help to maintain the general level in the soft 

 materials accumulated on the sea-bottom, and level plateaux of 

 limestone rocks may be formed by rock-boring animals eating 

 down the rock to the level of surrounding accumulations. Marine 

 shoals and sandbanks are commonly the joint production of wave- 

 currents and tidal-currents. The neutral wave-currents keep the 

 component parts in motion, whilst cross-tidal-currents accumulate 

 them. 



On the subject of the wearing of sand by marine action, evidence 

 is obtained from the Skerries shoal in Start Bay, where grains are 

 present in all stages of rounding, from the jagged fragment of quartz 

 with its angles just showing wear, to the perfectly smoothed and 

 polished spheroid. Some of the grains of sand exhibit a deposit of 

 secondary quartz, and not only has the original grain been worn, 

 but the crystalline encrustation also. The author believes that on 

 sandbanks where tidal and other currents keep in circulation a 

 small volume of sand, the rounding action of the waves is of im- 

 portance ; for, as he remarks, "The misinterpretation of the origin 

 of the constituent grains of a sandstone may result in utter confusion, 



1 On the Formation of Ripplemark, Proc. Royal Soc. vol. xxxiv. pp. 1-18. 



2 See paper "On the Influence of "Wave -currents on the Fauna inhabiting 

 Shallow Seas," Journ. Linn. Soc. (Zoology), vol. xviii. pp. 263-274. 



