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



point in Mr. Matthews's observations in the present connection is the 

 fact that he has found a stronger current at 70 metres than at the 

 surface. On this occasion, wliich was about the time of three-quarter 

 Springs, it amounted to as much as 13 miles per hour. In the pre- 

 ceding May,* he made, on the same station, a series of measurements 

 at 90 metres i.e. close to the bottom, extending through almost one 

 complete tide, but not, unfortunately, in quite sufficient detail to 

 admit of a resultant being taken. The force of current then measured 

 rose to as much as 0"5 mile per hour, and as it was only one 

 day subsequent to the date of the Moon's first quarter, one may 

 fairly safely assume at high Springs a bottom velocity, at this point, 

 reaching 1*5 knots or more. 



It is on this latter point that the main question turns concerning 

 the exposure of the stones. If it should be true, as evidence seems 

 to point, that there exists a constant tidal gain on the English side of 

 mid-Channel in a north-easterly direction, and in the more central 

 waters, as would seem from Mr. Matthews's observations towards the 

 south-east and south, this fact, combined with the presence of a 

 bottom current reaching as much as li knots, would be sufficient 

 to explain the exposure of stones. No fine deposit could accumulate 

 with this gradual shifting process constantly at work in the outer waters 

 of the Channel. It must be passed on elsewhere, perhaps to come to 

 rest ultimately off the English coast-line, or, on the other hand, it may 

 be, to be carried through the south towards the Atlantic. The evidence 

 afforded by the bottom-samples that were taken with the conical 

 and 1' 6" dredges tends to support this conclusion. Outside about ten 

 miles from the Eddystone no instance was found of what could, strictly 

 speaking, be called a fine deposit. Beyond this point the deposits obtained 

 might be described in general terms as coarse shell-sand mingled with 

 fine or coarse gravel and usually stones, with a very small proportion 

 of quartz grains. Except in sample (50), S. 16" W., 30'9 miles, the 

 material above 1 mm. in grade comprehended within the range of 

 Table II, amounted in all cases to more than 30 per cent of the 

 sample. In most of them it exceeded 50 per cent. Sample (50), 

 moreover, cannot by any means be regarded as of a fine grade, since 

 it also contained in addition to the finer deposit indicated in Table II, 

 several stones with an average greatest dimension of 6 cm.t Further, 

 it has already been pointed out (p. 109) that this coarser texture of 



* Id. May, 1905. Part B., p. 94. 



t The same point applies to several of these bottom-samples, in which the inclusion of 

 stones would have been too cumbersome for the purposes of Table II ; cp. especially 

 sample 79 (Table I, p. 116), where the larger stones averaged 0-67 lb. per stone. 



