396 Mr. S. V. Wood on the Belgian Equivalents of 



loping quartzite erratics, which seems to have induced Sir Charles 

 to hesitate in referring it to the horizon of the Boulder-clay, and 

 disposed him to place it as of somewhat later date, affords, how- 

 ever, to me the most satisfactory evidence that I can find of the 

 absolute identity between the Boulder-clay and the Loess, as well 

 as between the lower Drift of the Eastern counties and the Cam- 

 pinian sands of Belgium *. 



The extension of the lower Drift over Essex and Suffolk, and 

 the sharp though uninterrupted transition from it to the Boulder- 

 clay, having been described by me in the paper before referred 

 to, I cannot better show the position of the Campinian sands 

 relatively to the Loess, and the extension of both of these depo- 

 sits over Belgium, than by giving the substance of the descrip- 

 tion of M. d^Archiac in the * Histoire des Progres de Geologic.' 



M. d'Archiac f, after referring to the " Geest,'' which he de- 

 scribes as underlying the turf-beds and marsh clays of Holland, 

 as the only deposit in that country which, by its extent and 

 continuity, seems to belong to an earlier epoch, and to be the 

 result of a more general cause, quotes the description given by 

 M, Elie de Beaumont of the " Geest," as a vast deposit of 

 quartzose sand, sometimes slightly argillaceous, in a great part 

 of which occur small erratics, consisting both of chalk flints and 

 of fragments of crystalline rocks — a deposit occupying the sur- 

 face all over the countries of Liege, Juliers, Brabant, Gueldre, 

 Over Yssel, Westphalia, and Lower Saxony, forming extensive 

 heaths, and reaching to the border of the sea or to the edge of 

 the alluvial deposits of the low countries. M. d'Archiac then, 

 after observing that the " Geest " attaches itself in Belgium to 

 the sables de Campine, so widely spread in that country, hesitates 

 to express any opinion as to the age of the deposit, by reason of 

 the absence of sufficient evidence upon which one could be 

 based; and he then proceeds with the description given by 

 M. de Beaumont of the sands of North Germany, in which he 

 indicates them as extending from North Germany westward 

 without interruption past the Rhine, as far as the environs of 



* With respect to the erratics underlying the Boulder-clay, it may pre- 

 vent misapprehension if I observe that the terms upper and lower Drift, 

 that I have adopted to distinguish respectively the Boulder-clay and the 

 thick deposit of underlying sands and gravels, in no way represent the terms 

 " upper and lower erratics " adopted by the late Mr. Trimmer. The lower 

 erratics of that gentleman were the Boulder-clay (Quart. Journ. Geol. Soc. 

 vol. vii. p. 21), and the upper erratics {loc. cit.) gravel-beds described by him 

 as resting in places on the Boulder-clay. It would seem from the observations 

 of Sir Charles Lyell, which I have quoted, that this order of succession 

 weighed with him in forming an opinion as to the relationship between 

 the Boulder-clav and the Loess. 



t Vol. ii. pp.' 141, 142. 



