1 14 Mr. P. I. Martin's Observatiotis on the Anticlinal Line 



why the fissures remain, (to use the expres- 

 sion of jNIr. Scrojie,) " crevice-hke gorges," 

 insteadof opening into broad expansions, like 

 the longitudinal valley, produced by the op- 

 posite more sudden elevation. The curve 

 here pointed out may be represented as in the 

 margin. 



This carve brings the anticlinal line into 

 strict relation with'those masses composed of 

 concentric circles mantling round nuclei, 

 amongst the older formations ; and an ideal 

 section of it, whether longitudinal or trans- 

 verse, will exactly correspond v/ith sections of 

 such protrusions so often exhibited*. 



Assuming it therefore as proved, that the 

 strata above the chalk were continuous ante- 

 rior to the convulsion which threw diem, the 

 chalk itself, and the strata below the chalk, 

 into what has been called the basin shape, 

 it follows of course that the act of denuda- 

 tion begins with the upper beds, and pro- 

 ceeds downwards to the lowest that are here 

 exposed. And that the term denudation ought 

 not to be confined, as it has hitherto been, in 

 this instance, to the chalk and the Weald Val- 

 ley only, but is common to them all. Looking 

 more closely to the effect of this operation 

 upon each stratum in succession, we find ; — 

 first, that if any formation higher and less 

 ancient than the Bagshot sand, the strata of 

 Headon Hill, or the " upper marine" of the 

 London Basin, ever existed, it has been re- 

 moved entirely, or is hid beneath the sea ; and 

 that of the above named, a small portion only 

 remains. Of the London clay there is a larger 

 expanse beveled off at the edge, as almost all 

 clays are, and therefore presenting no escarp- 

 ment. The plastic clay comes next, and is 

 found to be in the same predicament, (except 



* I have elsewhere observed, that longitudinal and 

 transverse are merely conventional termsj as they apply 

 to the exposed or basset edges of strata (see note 1 of 

 my " Memoir") ; and it would be easy to show that 

 transverse valleys and a correspondent drainage are the 

 natural and necessary consequences of obliquities in all 

 protrusions ; or rather, that no elevation or subsidence 

 can exist without these conditions. 



where 



o 



