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



rate geological map of Belgium, by the late M. Dumont, indicates 

 in a still clearer manner the area occupied by the Campinian 

 sands and rolled stones, and by the overlying Loess, as well as 

 the relative positions of the two beds * ; and in the following 

 woodcut map 1 have reproduced, as well as the small scale will 

 allow, the destributiou of the two beds, as shown on the map of 

 M. Dumont, adding to it the area of the eastern border of Eng- 

 land, for the purpose of enabling a comparison to be made of 

 the distribution and position there of the Boulder-clay {h) and 

 underlying lower Drift {g), with the Loess and Campinian beds of 

 the Continent. In Belgium the grouping of the two deposits 

 shows that the valleys have been in some cases cut through the 

 Loess down to the Campinian sands, where that deposit underlies 

 the Loess, as, for instance, in the neighbourhood of Brussels and 

 of Bilsen ; but in this respect the grouping of the beds is much less 

 striking than in the case of the eastern counties of England. The 

 coincidence between the valleys cut through the Loess and those 

 of England, in point of time and mode of origin, is shown in a 

 way that the limits of this paper do not permit me satisfactorily 

 to enter upon. In the paper on the formation of the valleys, 

 before referred to, I attempted to show that the valleys of the 

 east of England, which cut through the upper and lower Drift 

 of that region, resulted from the denudation having been regu- 

 lated by the disturbance of the floor of the sea of the upper Drift, 

 which took place in the form of a series of circular movements. 

 The more important of these movements affecting that part of 

 England originated in three centres, one of which was near 

 Canterbury, another immediately south of the Isle of Wight, 

 and another in the North Sea, off Flamborough Head f. 



So far as I have been hitherto able to trace them, the circular 

 movements emerging from these three centres, with others of 

 similar character and simultaneous origin emerging from centres 

 on the Continent, appear wholly to have formed the valleys which 



* The three deposits are by him placed in the following descending order : 



Loess {limon Hesbayen) ; 



Sables Carapiniens ; 



Cailloux roules. 

 t Although these three series form the principal valleys of this part of 

 England, a close investigation of the Ordnance Sheets appears to disclose 

 other inequalities of surface, that are parts of circles originating at much more 

 remote centres, and whose effect has, from distance, become proportionately 

 feeble. I hope at a future day to show the whole grouping of these circular 

 phenomena, and the effect of their reciprocal pressure in France and Bel- 

 gium, as well as in England, and the manner in which, in the south of this 

 country, subsequent but more localized and powerful movements have su- 

 pervened on them. The short notice of them published in the ' Phil. Mag.' 

 is very incomplete, and in some respects imperfect. 



