202 H, M. Jenkins — Surface Geology of Belgium. 



d'Omalius d'Halloy ; but I venture to think that the physical rela- 

 tions of the deposits prove the higher antiquity of the Limon 

 de Hesbaye. The importance of the question, however, should lead 

 to further investigations than my agricultural engagements left me 

 time to prosecute. Mr. Godwin -Austen, in his paper " On the 

 Kainozoic formations of Belgium," remarks' : — " The age of the 

 Campine sands has been very often discussed. They are now very 

 generally referred by Belgian geologists to the Systeme Diluvien. 

 Though the true Campine sand has never been found to contain 

 animal remains of any kind, it overlies a surface with ElepJias primi- 

 genius. It is certainly older than the Polder mud deposits and their 

 equivalents, the peat growths. However, there may still be a great 

 range between these extreme periods. In like manner, the Loess 

 (Limon de Hesbaye) overlies the gravel beds in which the fragmentary 

 remains of the great Pachyderm fauna occur. Both the Campine sands 

 and the Loess are subsequent accumulations to the Ardennes quartz 

 pebbles ; but the occurrence of these pebbles at the base of both does 

 not necessarily connect them with either, but it suggests that these 

 two accumulations must be nearly of the same age, and such, it 

 seems, was M. Dumont's latest view." 



The occasional occurrence of freshwater and land shells (Succinea, 

 Pupa, &c.) in the Limon de Hesbaye has led to the opinion that the 

 whole mass is of freshwater origin. I find it difficult to subscribe 

 to this view, and still more so to that which ascribes a contempo- 

 raneous formation to the Loess and the Campine sands ; as in that 

 case the sand must have been deposited in the deeper water ! 



With reference to the causes which have produced the present 

 " form of the ground " in Belgium, these terraces seem to me to 

 demonstrate the truth of Professor Eamsay's idea of ''planes of 

 marine denudation,"^ so far, at least, as that country is concerned ; 

 and in the accompanying section I have shown by a dotted line 

 where I conceive the planes of marine denudation left the surface of 

 the country to have its present physiognomy chiselled out by the 

 force of subaerial agents.^ 



The delineation of the contour lines on a map of the surface- 

 geology appears a most important adjunct. In the map of Bel- 

 gium, it is instructive to observe the remarkable coincidence in 

 the " behaviour " of the contour lines and in that of the geological 

 boundaries, and especially how they similarly become squeezed 

 together in the east and widen out in the west. The whole country 



' Quart. Journal Geol. Soc, vol. xxii., p. 250. 



2 A somewhat similar view of another region has been proposed by Mr. G. A. 

 Lebour to explain the surface-features of Western Brittany. (See Geol. Mag. 

 Vol. VI. 1869, p. 442.)— Edit. 



3 May we not regard the far greater diversity {i.e. the more denuded character) 

 of the surface covered by the Limon de Hesbaye than of the Campine sand region 

 as an additional piece of evidence in favour of the previous denudation of the former 

 region. The eminences in the loamy region are numerous, and not unfrequently 

 rise to a height of from 300 to 400 feet above the neighbouring valleys, while in 

 the Campine sand district a difference of level of 30 feet cannot be seen except in 

 the extreme east — the true Campine. 



