ON ROCK REMAINS IN THE BED OF THE ENGLISH CHANNEL 101 



outside the Eddystone, the dredges revealed nothing but clean shell- 

 sand. Outside it, however, from the time when the gear was 

 suitably adjusted to the work, there was no single point among the 

 forty-five positions in which either of the larger dredges was used 

 where stones were not found in greater or lesser degree. It may 

 therefore be said that outside this 15 -mile point a stony area was 

 traced without interruption for a distance of 34 miles S.S.W. and for 

 some miles to the eastward and westward of this line, covering a total 

 area of some 300 square miles. At Position (80), the outermost point 

 reached, bearing S. 16° W., 49 miles, which is slightly beyond the 

 middle of the Channel, both the average size and the average weight 

 of the stones collected were, with one exception, higher than anywhere 

 observed, and there is every reason to suppose that beyond this point 

 similar conditions prevail to within close proximity to the French 

 coast. 



(2) Intensity. — Of the distribution of the stones exposed in point of 

 intensity it is more difficult to speak with assurance, so many are the 

 factors which must enter into consideration : the character and possi- 

 bilities of the gear employed, the variation of local conditions, and the 

 tendency of the dredge to become quickly filled with animal debris in 

 a particular spot, the general success of a haul dependent on tidal and 

 weather conditions ; all these tend to complicate the result as shown 

 by the stones actually taken ; so that it is difficult to form a just 

 quantitative estimate without a more complete and systematic 

 method of investigation than was possible in the circumstances. 

 From the available data, however, there is little doubt that the 

 stones lie scattered about the surface, with very little interruption 

 over the whole area. In a table appended below (Table I, p. 114) 

 detailed particulars are given of every sample obtained, including 

 the estimated area covered by the dredge used. This estimate as- 

 sumes an average rate of towing of one sea-mile per hour throughout. 

 This cannot be regarded as more than a rough approximation, but it 

 is sufficiently near for the general purpose. Excluding three hauls 

 where no definite result was obtained owing to the dredge being fouled 

 on obviously rough ground, the total area actually covered by the 

 remaining 53 hauls amounts on this estimate to 11,950 square yards. 

 The total number of stones of 4 cm, and over that were collected 

 being 5808, an average ratio of distribution is obtained for the whole 

 area of 0"5 per square yard. 



Probably this estimate is somewhat short of the true state of things, 

 for it does not take into consideration those stones which are too large 

 to enter the opening of the dredge, nor does it make allowance for 



