2 



Mr. A. R. Hunt. 



[Apr. 20, 



change of wind (" Elements of Geology," 6th edition, p. 19). Mr. J. 

 Beete Jukes, in the first edition of his " Manual of Geology," states, 

 that current mark or ripple "is produced on the sea beach, not in 

 consequence of the ripple of the wave impressing its own form on the 

 sand below, which would be an impossibility, but because the moving 

 current of water as the tide advances or recedes produces on the 

 surface of the sand below the same form as the moving current of air 

 produces on the surface of the water above. A rippled surface, there- 

 fore, to a rock is no proof of its having been necessarily formed in 

 shallow water, though rippled surfaces are perhaps more frequently 

 formed there, but simply a proof of a current in the water sufficient 

 to move the sand at its bottom gently along, at whatever depth that 

 bottom may be from the surface of the water." Speaking of fossil 

 ripplemarks the same author states that the distance from crest to 

 crest of the ridges varies from half an inch to eight or ten inches, 

 wi f h a proportionate variation in depth between them (Jukes' " Man. 

 Geol.," p. 172). The article on ripplemark is recast in the third 

 edition, edited by Dr. Geikie and published in 1872, but the views 

 expressed therein are the same. 



Monsieur Delesse goes far beyond the authorities referred to above, 

 as on the authority of Commandant Cialdi, he states that the move- 

 ment of waves can displace fine sand at a depth of 200 metres in the 

 ocean, and (without giving his authority for the statement) that the 

 undulation of the sea is evidenced by ripplemarks on muddy bottoms 

 down to a depth of 188 metres (" Lithologie du fonds des Mers," 

 1871, pp. 110, 111). More recently, Mr. G. H. Darwin has stated 

 that one of the conditions of the formation of many ripples is a great 

 ebb and flow of the tides (" Nature," vol. xxv, p. 214). 



It will be seen from the authorities cited above, that the pheno- 

 menon known as ripplemark is variously ascribed to the action of 

 currents, and to the undulation of waves, and that whereas by some 

 it is considered the result of tidal action in shallow water, by others 

 it is attributed to the action of waves down to the great depth of 

 upwards of 100 fathoms. 



I shall endeavour in the present paper to prove that ripplemarks 

 formed under water are, as a rule, completely independent of the rise 

 and fall of tides, of tidal currents, and of sea beaches ; and that they 

 have little in common with the current mark, that owes its origin 

 either to a continuous current of air or of water. 



For some years past I have neglected no opportunity of making- 

 observations on the action of storm waves on the bottom of Torbay, 

 and of collecting evidence as to the action of waves and currents on 

 the bottom of the English Channel. To Lord Rayleigh I must express 

 my indebtedness for having examined my evidence of submarine wave 

 action from a mathematical standpoint, and for having called my 



