504 S- V. Wood— The Valley System of 8.E. of England. 



Lave been due to a force which, it seems to me, can only have been 

 steam rising obliquely at each of these three centres, and pushing 

 the strata laterally outwards from the point where the impulse 

 originated ; causing them to fold along successive arcs, which are 

 very much in appearance like the circles which spread out from the 

 place where a stone is thrown into the water, save that they are not 

 in any case complete circles. In the case of those spreading from 

 the Isle of Wight centre they are semi-circles ; but in the case of 

 those spreading from the Canterbury centre they are only quadrants 

 of ellipses. 



Whether they agree with me or not, those gentlemen who assume 

 to teach us the way in which mountain chains have originated, and 

 the mode in which the disturbance of strata has come about, do most 

 certainly remain in ignorance of one of the factors of the problem 

 which they seek to elucidate, unless they master the details of the 

 map which I, by presenting to the Geological Society, endeavoured 

 to place so many years ago at their service. 



In conclusion, I would observe that in the paper of 1864 I 

 regarded the period at which these arc disturbances took place as 

 having been the " Glacial " ; and I attempted to connect with them 

 the position occupied by the " drift " in the East of England. In 

 his communication to which I have referred, Mr. Dalton makes the 

 same connexion, and refers the "wave" (as he calls it) of disturb- 

 ance which produced the fold at Wickham to the same period ; but 

 I long ago satisfied myself that in this I was in error, and that the 

 movement was altogether pre-glacial ; having, I think, originated 

 under the older Tertiary sea-bed. A set of rectilinear disturbances 

 giving rise to the highly inclined axis of the Isles of Wight and 

 Purbeck, and to the Hogsback of Surrey, did, however, as it seems 

 to me, take place during the Glacial submergence ; and these by 

 supervening on the anterior arc-shaped disturbances have, where 

 they crossed the arcs, shifted the strata, and given rise to faults, 

 such, e.g. as that at the western extremity of the Hogsback.^ 



1 These rectilinear disturbances are shown, in the map to the paper in the Phil. 

 Mag. of March, 1864, by a different shading to that of the arc disturbances. The 

 hypothetical line of section carried as a radius through the successive arcs of the 

 Canterbury system (Sect. No. 2 of the Phil. Mag. plate), passes only eight miles 

 W.S.W. of Wickham ; the fold of which that now disclosed at Wickham forms part 

 being shown in this line of section at Galleywood, but in the MS. map this is 

 corrected by the arc being shown to pass through Danbury. The Wickham part of it 

 is immediately north of the point where the confluence of the rivers Chelmer and 

 Blackwater takes place in a breach through this arc, caused by the transverse action 

 of the arcs spreading from the Isle of Wight and North Sea centres. The fold, at 

 Eoyston, is part of that crossed in the radius section at Baldock, about the same 

 distance W.S.W. of Eoyston that Galleywood is of Wickham. The points in the 

 radius section at which the folds giving rise to the arc ridges should occur are shown 

 by corresponding folds in the dotted lines over it, the character of the fold itself in 

 hard strata, such as the chalk at Eoyston, and beneath Wickham, being shown by 

 a separate diagram. In the volume of this Magazine for 1866, pp. 350-2, where I 

 entered at some length into the subject of these arcs (connecting erroneously the move- 

 ment in which they originated with the time and mode of the gravel accumulation), 

 I drew the section (No. 9 of the plate) which I there gave across the arc in question 

 through the Trigonometrical Station at Wickham Bishop ; and showed by dotted Lines 



