THE UNDULATIONS OF ITIK CIIAI.K. IN ESSEX. II5 



It will be seen that about Ware, at Bishop's Stortford, Sudbury, 

 and Ipiswich, the Chalk boundary is very sinuous, whilst between 

 those points it forms curves for the most part broad and smooth. 



That is simply due to our knowledge at the points mentioned, and 

 our ignorance as to the intervals. We do not know what sinuosities 

 are present under the pall of drift, and w^e can only carry the hypo- 

 thetical line between sections that prove the absence of Tertiary beds 

 to the north, and their presence to the south. Lately a well sunk 

 northward of the boundary assumed in the (Geological Survey map 

 at Little Sampford proved the further extension of the Tertiaries. 

 Such corrections (or their converse, the reduction of the hypothetical 

 area of Tertiary beds) are most welcome and useful. The general 

 strike is E.N.E. from Ware to Sudbury, and thence E. to Bramford. 

 Beyond the limits of the map, it runs N.E. to Saxmundham, and N. 

 to Yarmouth. 



The base of the Chalk is approximately parallel to this line, and 

 so is the the great faulted undulation of Tiptree Heath, which I 

 described several years ago.^ 



That important flexure has quite recently been again proved at 

 Messing, and its course through Suffolk is traceable at Shelly, Ipswich, 

 Woodbridge, and Lowestoft. Along Tiptree ridge it is a faulted 

 anticlinal for several miles. From Wickham Bishop it is traceable 

 with less distinctness by Danbury to the south-west, its effects being 

 complicated by a series of obliquely-transverse flexures and fractures 

 in a manner defying verbal description. The parallel fault from 

 ^V'alton to Prittlewell, the anticlinal of Mersea and Burnham, and 

 the bold flexure at Royston (where the Chalk dips at 40^ to N.N.W.) 

 point to some general agency affecting a wide area, and in like 

 manner the east and west fractures from Greenwich to Erith, and 

 ^Valthamstow to Burnham, are probably of the same age and origin as 

 the parallel anticlinals of the Stour estuary (not shown by the contours), 

 and that in which Bentley occurs (as indicated by the zero-line.) 



The lines of flexure and fault of N.W.-S.E. trend are less regular, 

 of shorter continuance and variable direction, and appear to be the 

 result of transverse strains at the time of the later of the previously- 

 mentioned movements in a district weakened by the earlier series. 

 It seems probable, for instance, that the triangular bit of country 

 between Chigwell, Havering and Romford was crushed into its 

 present structure of anticline and syncline by pressure from the 



3 Trans Essex Field Club, vol. ii, pp. 15-18, iS3i. 



