6 



Mr. A. R. Hunt. 



[Apr. 20, 



In a paper published in 1859 * Mr. H. 0. Sorby, F.R.S., showed 

 how currents flowing in one direction form the kind of ripplemark or 

 current mark termed by him " rippledrift ;" but, as the currents that 

 form the ripplemarks on the sea-shore are alternate and set up no 

 drifting action in the ordinary sense of the word, it seems to me 

 important to distinguish between the current mark that can be seen 

 occasionally on the bottom of running water and the marine ripple- 

 mark that differs from it, both as to its origin and as to its effect. I 

 believe the symmetrical ripplemark of the sea-shore cannot be formed 

 by a continuous current, and that whether recent or fossil it is as 

 certain an indication of an alternate wave current as the " ripple- 

 drift " is of a continuous current. Both of these current marks can 

 be readily formed in a round tub of water with a little sand on the 

 bottom. If the water be rotated constant- current ripples or " ripple- 

 drift " are formed : if the tub be carefully rocked symmetrical alter- 

 nate-current ripples shortly appear. 



My experiments having satisfied my mind that ripplemark can be 

 formed on sandy bottoms by a slight oscillation of the water, I took 

 an early opportunity of visiting the shores of Torbay, between Torquay 

 and Livermead Point, for the purpose of ascertaining definitely 

 whether the size and direction of natural ripplemarks bore any rela- 

 tion to the force and direction of the wind. The day selected was the 

 21st January, 1882, after a week of calm weather, accompanied by the 

 highest recorded rise of the barometer in Britain. There had been 

 very little wind for days, but a slight swell on the 20th, and very low 

 tides promised a well-rippled beach for the 21st. 



On reaching the sands under Sulyarde Terrace, I observed that they 

 were covered with the most perfect and symmetrical ripplemarks from 

 the south-west, the only direction from which a swell from the sea 

 could reach them, as the new pier, protects that part of the shore from 

 waves coming from any point more to the southward. Proceeding 

 thence along the sands in a westerly direction, I saw the ripplemarks 

 gradually getting effaced, until at a point opposite the Belgrave Road 

 they were completely obliterated, excepting in pools and depressions in 

 the sand, where they were as perfect as before. At this point, which 

 is not protected by the pier and is exposed to the open sea, the direc- 

 tion of the ripples was south-south-east (S.S.E.). In one of the pools 

 they measured 6 inches from ridge to ridge, and the ridges were 

 sharply defined and perfectly angular. Under the Corbons, on a little 

 beach between the rocks, there were some very perfect ripples 13 inches 

 between ridges, and If inches in vertical height. Passing on to the 

 next beach, Livermead Sands, I found a large area of sand covered by 

 perfect 6-inch ripples from the south-east, which in their turn were 



* " On the Structures produced by the Currents present during the Deposition 

 of Stratified Rocks." " The Geologist," 1859, p. 137. 



