112 Mr. P. J. Martin on the Anticlinal Line of 



direction of the valleys running towards the Thames from the 

 North Downs, and from the South Downs towards the sea, and 

 taking the sweep of their long-extended slopes. He will now be 

 in the best condition for studying tbe more complicated gravels 

 of the valley of the Thames, or the drift generally of both the 

 great synclinals. 



I shall hail the appearance of Mr. Prestwich's publication with 

 much pleasure. I venture to predict that it will be characterized 

 by the careful research and correct analysis that distinguish the 

 writings of that gentleman. He will assign to the eocene shin- 

 gle, to the angular ilint, and to the " northern drift," their proper 

 share in the general mass, and their proper sources. He will 

 show from whence the materials foreign to tbe stratified beds of 

 the " London basin " were derived, and perhaps venture some 

 speculations respecting the boulder clays. He will intercalate 

 here and there some fragment of a stratified bed of the older or 

 newer pliocene. But will he tell us to what agencies we owe 

 the intermingling of these discordant materials ? Why have we 

 "drift," or more properly and significantly speaking, a "terrain 

 de transport" ? And still more pointedly, why do we find in the 

 vicinity, and at the same level, a large district almost devoid of 

 drift foreign to itself, — a district out of which everything has 

 been taken and nothing carried in, — a district in which are 

 written in the strongest characters the words demolition and 

 forcible denudation ? 



On some specialities ivhich militate against, or at least tend to 

 modify the doctrines of the foregoing pages. 



There was so much fascination in the first and original idea, 

 that the great excavation of the Weald and all its attendant de- 

 nudations were the work of one gi'cat, and though it might have 

 occupied much time, one uninterrupted process (jf joint terrene 

 and aqueous convulsion, that it was long before I felt disposed to 

 admit the possibility of several acts, all of the same paroxysmal 

 nature and tending to the same ends. That these acts or inter- 

 missions in the great drama were diversified by the growth of 

 terrestrial surfaces, and the existence of an intermediate fauna, I 

 have now not much doubt. 



I had long been familiar with Sir H. Englefield's 'Isle of 

 Wight,^ and with Webster's 'Survey;' but I thought, and per- 

 haps I still have reason to think, that the appearances there of 

 intermediate terrestrial surfaces might be reconcileable with the 

 opinion I entertain of a diversity of land and sea at the time of 

 the corameucemcut of the tera of dislocation. 



I do not take the phaenomena of the Isle of Wight or of raised 

 beaches on the Devonshire coast into my review ; but I admit 



