34 G. H. KINAHAN ON THE CHESIL BEACH, DORSETSHIRE, 



windward or leeward respectively, if the tidal current or wind- waves 

 have the greater power. In the latter case, if the cargo " breaks 

 loose " it will be carried, if not very heavy, by the wind-waves ; 

 heavy cargoes, such as coal, if the gale be continued, will be more 

 or less carried to leeward, but eventually will go with the tidal 

 current; a cargo of green timber or "pit wood," as it floats just at 

 the surface, is usually stranded to windward, having been carried 

 by the tide against the wind- waves. "While examining into the rela- 

 tive driftage powers of wind-waves and tidal currents, there is one 

 kind of the latter nearly always ignored ; that is, the current due to 

 the on-shore set of the offing tide. A wreck may be off the coast and 

 the wreckage drifting, say northwards, across a gale from the east 

 or north-east ; it will be carried in that direction for half tide (three 

 hours) ; but after the offing tide sets in, it wilJ be carried to the 

 shore. This on-shore driftage is usually supposed to be due to the 

 wind ; and fishermen explain it thus : — " The wind has no force till 

 half the tide is gone." 



Second Point. — " Flow and ebb of the tide are equal and opposite, 

 and therefore counteract one another's effects." Let us examine 

 into certain effects of the ebb and flow of the tide which can be dis- 

 tinguished. On a calm day, when there is not a ripple on the water 

 nor a perceptible ground-swell, if the tide is ebbing it imperceptibly 

 drops away from the shore, leaving every thing undisturbed. If, 

 however, it is flowing, the strand under similar circumstances gets 

 saturated with water before the waves go over it, which causes each 

 particle to be more or less buoyant ; so that even in low neap tides, 

 where the current is least, fragments of considerable size will be 

 moved, although only an inch or two. During spring tide, the in- 

 coming tidal current is greatest ; therefore it might be supposed that 

 the outgoing current also would be greatest at this state of the tide ; 

 yet under such circumstances we find the water drop away from the 

 shore without disturbing those portions of the beach that are never 

 uncovered except during " spring tides." This of course only refers to 

 ordinary coast-lines ; as in " narrows," and round certain points there 

 are ebb-tide currents which effect considerable local driftage. Further- 

 more, in estuaries and bays the mud and sand banks always indicate, 

 from their shapes and positions, that they are more due to the flow 

 than the ebb of the tide. This is to be seen even in estuaries into 

 which large rivers flow, and in which the ebb tide is there aug- 

 mented. It may also be pointed out that the margin of the flow 

 tide, no matter how calm the water may be, is always more or less 

 " dirty " (with fragments of seaweed and such like) ; but this dirt is 

 left behind when the tide ebbs. The flow tide when it comes to a 

 stranded obiect pushes it before it ; but a slight resistance will pre- 

 vent a similar object from being dragged out by the ebb. 



When the flow tide is helped by the wind its effects are con- 

 siderably increased ; but wind-waves do not proportionally aug- 

 ment the ebb tide. This can be seen during a moderate gale of wind, 

 when waves are breaking on a beach. If the tide is flowing, the 



