110 ON ROCK REMAINS IN THE BED OF THE ENGLISH CHANNEL. 



In most of the samples the smaller particles, both organic and 

 inorganic, show a good deal of rounding and often a high polish, and in 

 all of them there is almost or entirely an absence of silt.* 



Few as these samples are and irregularly disposed over so great a 

 distance, the fragmentary evidence afforded by them is important in 

 its bearing on the final question to be dealt with. 



(6) Conclusion. — One point remains to be considered in conclusion. 

 How is the exposure of these stones at the present time to be 

 accounted for ? The Channel bottom is probably disturbed to a con- 

 siderable depth by wave action in stormy weather, though to what 

 degree is a matter yet to be investigated. Fine particles of sand and 

 other matter have often been taken in the tow-net at a considerable 

 distance from the bottom, and even at the surface, in water as deep 

 as in any part of the Channel. It would be difficult not to attribute 

 this, in some degree, to wave action. It is commonly asserted by 

 fishermen that on the trawling-grounds off the Start, in 35 to 40 

 fathoms, they are much more liable to have their trawls fouled by large 

 stones immediately after stormy weather than at other times, the belief 

 prevailing that at such times the boulders become more exposed owing 

 to the disturbance of the fine deposit. A case in point occurred quite 

 recently (December 15th, 1907), after an exceptionally rough spell of 

 weather, when some of them encountered heavy stones on these 

 grounds, and by one of them, the Brixham trawler Love and Unity, 

 a block of granite was brought into Plymouth weighing 833 Ibs.f 

 Probably there is much truth in this impression, and the influence of 

 wave action should be considered as partly contributing to the con- 

 tinued exposure of the stones far out in the Channel. But the direct 

 agent must be sought for in the tides, and I think it will be found that 

 the tidal conditions in this region are sufficient to explain the cause at 

 work. 



As far at least as about the 40-mile point referred to in these 

 cruises, there appears to be a constant gain on every complete tide in 

 a north-easterly direction. The meridian of the Eddystone is roughly 

 the western limit of the conflicting tidal conditions caused by the 

 Dover Stream, involving at intervals an opposite direction of the 

 current in the easterly and westerly portions of the Channel. When 

 in this westerly part of the Channel the tide turns to flow, it has to 

 encounter,, to the southward of the Eddystone, a still strongly ebbing 

 stream from Dover. Aided by the northerly set from the Bay of 

 Biscay, it is forced against this in such a way as to be deflected to the 



* i.e. matter which remains in suspension in water at the end of one minute, 

 t This stone is referred to by Mr. Worth on p. 122. 



