Hunt — On the Action of Waves on Sea-beaches, 8fc. 281 



deep enough to reacli the bottom, but passes over it as a surface 

 current, the object will escape any direct action, and may even be 

 impelled in a direction contrary to that of the main current by an 

 under-current moving seawards, to balance the main surface-current, 

 moving shorewards. Thus the difference of a few feet in the depth 

 of a current may make all the difference in the direction in which 

 a light object on the bottom may travel under its influence. 



The action of the waves on shells, such as the cockles already 

 referred to off Paignton, lying, as the latter occasionally do, in six- 

 fathom water, at the foot of the slope rising towards the shore, 

 would naturally be much affected by the depth of any surface- 

 current that might be driven into the bay. If deep enough to 

 reach the shells, the wind-current would unite with the breakers in 

 driving the shells up the slope shorewards. If not deep enough to 

 reach them, the surface -current shorewards would generate an 

 under-current seawards, which would oppose the shoreward impulse 

 of the breakers. When such conflicting forces are at work it is not 

 surprising that shells should be cast on shore by one gale and not by 

 another, or that they should be abundant on certain beaches, whilst 

 almost, if not quite, absent on others in the same neighbourhood. 



It seems unnecessary to adduce further evidence in proof that 

 a wind blowing into a bay may set up currents both in its own 

 direction and in a direction opposed to its own. The fact is one 

 of common acceptation, as evidenced by the statements of Messrs. 

 Dana and Greikie in their respective manuals, as already quoted, 

 viz. " The forcing of water into bays .... causes a strong current 

 outward," and " A prevalent wind, by creating a current, .... will 

 cause the shingle to travel coastwise." But in this admitted 

 action of the wind in causing currents we have, as it appears to me, 

 an explanation of the apparent paradox, that winds and waves oc- 

 casionally appear to drive large pebbles further than small, and at 

 other times small pebbles further than large. 



In the passage already quoted (P. 31), Admiral Spratt bears 

 witness to the fact that he has seen small clinkers travel along a 

 coast faster than large ones ; but all sizes travelled in the same direc- 

 tion. Mr. W. Topley, describing the beaches between groynes 

 on the coast of Sussex and Kent, stated that " in each separate 

 area it was found that the largest pebbles had been carried ... to 

 leeward, and to the summit of the beach" (P. 25). These cases 



