THE 



GEOLOGICAL MAGAZINE, 



NEW SERIES. DECADE II. VOL. IX. 



No. X.— OCTOBER, 1882. 



oi^zo-iit^^Ij .a.s,ticii.:h]s. 



I. — Traces of a Great Post-Glacial Flood, 



4. Evidence of the Angular Drift. 



By H. H. HowoRTH, F.S.A. 



'E have sifted the evidence furnished by the Loess, by the loams 

 and brick-earths, and by the valley terraces which are such 

 conspicuous features in the surface geology of Europe, and we have 

 found them furnishing a perfectly consistent and perfectly reasonable 

 story. We have still left for consideration the most eloquent for 

 our purpose of all the surface deposits, namely, the great sheets of 

 angular gravel which many of us have examined with curious 

 interest for many days, and which mantle so much of the land on 

 either side of the English Channel. 



The chief characteristic of this gravel is that it is for the most 

 part composed of broken flints with un rubbed edges, whence Mur- 

 chison called it the Angular drift. This character it bears on both 

 sides of the Channel ; and there can be no doubt that as it occurs at 

 Sangatte, etc., where it has been described by M. d'Archiac and 

 Mr. Prestwich, it is, as those authors urge, identical in origin with 

 the drift capping the cliffs at Brighton and at Bournemouth. This 

 drift has given rise to much discussion, and, as in previous papers, 

 we will first examine the theories which have been recently current 

 about it, and conclude with our reasons for adopting a wide-sjDread 

 inundation as the vera causa alone competent to meet its conditions. 

 Every inquirer who has examined the question is agi'eed upon one 

 fact, which is indeed palpable, that the flint drift we are discussing 

 was distributed as we now find it by water. Once it was supposed 

 that it was a marine deposit, but this view is no longer held any- 

 where. The fact that the flints are for the most part unrolled quite 

 takes the deposit out of the category of a marine shingle, nor again 

 do we find in it such traces of marine organisms as would inevitably 

 be present if it had been a marine deposit. Upon this point Mur- 

 chison's observations are most just. He says: "If an arm of the 

 sea had permanently occupied this tract during each of the long 

 periods in which the advocates of gradual causation suppose the 

 strata to have been successively broken, crumbled down and washed 

 away, we ought to find some relics of the water-worn shingle, of 

 former times, along the numerous escarpments of Upper and Lower 

 Greensand, etc., if not along the edges of the escarpments of the 

 chalk or chief shores of former seas. But if not along those main 



DECADE II. — YOL. IX. — NO. X. 28 



