Ch. XIII.] DERANGEMENT IN THE CRAG STRATA. 177 



rows had occupied. Many grains of sand were drifted along 

 the slopes a b, and c d t which, when they fell over the scarps 

 b c, and d c, were under shelter from the wind, so that they 

 remained stationary, resting, according to their shape and 

 momentum, on different parts of the descent. In this manner 

 each ridge was distinctly seen to move slowly on as often as 

 the force of the wind augmented. We think that we shall 

 not strain analogy too far if we suppose the same laws to 

 govern the subaqueous and subaerial phenomena ; and if so, 

 we may imagine a submarine bank to be nothing more than 

 one of the ridges of ripple on a larger scale, which may increase 

 in the manner before suggested, by successive additions to the 

 steep scarps. 



The set of tides and currents, in opposite directions, may 

 account for sudden variations in the direction of the dip of the 

 layers, as represented in the wood-cut, No. 33, while the 

 general prevalence of a southerly inclination in the Crag of 

 Suffolk may indicate that the matter was brought by a current 

 from the north. 



We may refer to a drawing given in the first volume*, to 

 show the analogy of the arrangement of the submarine strata, 

 just considered, to that exhibited by deposits formed in the 

 channels of rivers where a considerable transportation of sedi- 

 ment is in progress. 



Derangement in the Crag strata.' In the above examples 

 we have explained the want of parallelism or horizontality in 

 the subordinate layers of different strata, by reference to the 

 mode of their original deposition ; but there are signs of dis- 

 turbance which can only be accounted for by subsequent move- 

 ments. The same blue and brown clay, or loam, which is often 

 perfectly horizontal, and as regularly bedded as any of our 

 older formations, is, in other places, curved and even folded 

 back upon itself, in the manner represented in the annexed 

 diagrams. 



* Chap, xiv., Diag. No. 6. 

 VOL, III. N 



