ON ROCK EEMAINS IN THE BED OF THE ENGLISH CHANNEL. 107 



as large as 90 cm. and 50 cm. being taken. But it is signijficant that 

 in forty-five hauls with these three dredges, no stones with any 

 approach to such a size, even in their greatest dimension, were 

 obtained. Among the largest were — 



four of 20 cm. on (19), (77), and (58) 

 five of 21 „ „ (19), (58), and (62) 

 four of 22 „ „ (19), (53), and (67) 

 one of 26 ,, ,, (58) 

 two of 27 „ „ (53) and (80) 

 one of 30 „ ,, (77) 



It may therefore be concluded that, except, of course, in so far as 

 they are largely or wholly covered up, very large stones are not very 

 numerous in this area, and the dimensions and weights shown on the 

 curves may be taken as a fair approximation to the true average. 

 There is no doubt, however, that very large stones and even boulders 

 do occur with considerable frequency, as on the trawling-grounds off 

 Start Point. The heavy working of the dredge communicated through 

 the warp, the breaking of the safety-stop, and the bending or even 

 breaking of the ironwork of the dredge afforded frequent evidence of 

 this. A broken stop occurred at the following points : — 



(38), S. 381° W., 22-2 miles 

 (39), S. 38° W., 22-2 „ 

 (18), S. 29° W., 23-4 „ 

 (62), S. 25° W., 46-4 „ 



At (21), S. 25° W., 21-2 miles, the 3' 0" dredge employed was brought 

 up fast and lost, only a portion of one arm being recovered. 



To break the safety stop, a strain is required of some 600-700 lbs- 

 To sharply open out the wrought-iron frame of the dredges used, in 

 the manner that too often occurred, involves a strain of several 

 hundredweight; while in the total loss of the dredge at (21), the part- 

 ing of the remaining arm would only be caused by a strain of about 

 twelve tons. At some of these points, then, and at (21) in particular, 

 heavy boulders must have been encountered, the size of which can 

 only be estimated at a rough minimum. 



As regards the second point, the position of the stones as they lay 

 when dredged up, there is ample evidence to show that, with very few 

 exceptions, they were well exposed at the surface of the sea-bottom, 

 and that they have probably so lain for a considerable time past. 

 Almost without exception, they supported living animal growth or 

 its remains— Porifera, Hydrozoa, Polychteta, Polyzoa, MoUusca, etc. 

 Scarcely any of the stones were without investing Polyzoa, which 

 often covered the greater part, sometimes the whole, of the surface. 



