Chalk Strata of Ballard Head. 



463 



account for the flints of the upper chalk, and the want of flints 

 in the lower, or those siliceous particles occasionally inter- 

 spersed, without any definite congregation of them, in certain 

 intermediate beds at Harwich* and Lyme? But, as there is 

 no known similar example of the phenomena of Ballard 

 Head, considering, also, the peculiar condition of the inferior 

 adjacent rocks, it is more correct to assume that the solution 

 of the difficulty is to be sought in some such nsoay as Mr. 

 Webster suggests in Jig. 45., though to me that particular 

 explanation is perfectly unsatisfactory. 



The authors of the Outlines being of the same opinion, 

 accordingly propose the following as another solution. They 

 observe that "the horizontal strata suddenly turn upwards 

 into a curve forming nearly a quarter of a circle (see Jigs. 36, 

 and 37.), and the vertical layers of flint meet the bent part 

 of the chalk, as so many ordinates would meet a curve, de- 

 creasing in height as they get more under it. Mr. Webster 

 has proposed an ingenious, but perhaps not altogether satis- 

 factory, solution of this remarkable position." (See Jig. 43., 

 and the observations upon it.) " Instead of repeating this, we 

 shall attempt to show, that it may be simply and completely 

 accounted for by the obvious supposition of such a fault, or 

 dislocation, of the strata, as is familiar to all geological en- 

 quirers, and, considering the angular motions which these 

 masses of strata have undergone, might naturally be expected 

 here : for this purpose we must have recourse to a diagram." 



" Let a b (Jig. 4^6.) be the assumed line of fault; then 

 let the mass of strata a b c be moved along it in the direc- 



* Mentioned in a paper by the author, " On the Geology of Suffolk, 

 read before the Geological Society, March 8. 1837. 



