H. M. Jenkins — Surface- Geology of Belgium. 199 



these points have received confirmation, as time flowed on, from 

 nearly all the most trustwortliy of his contoinporarics. 



So lately as February, 18G7, the Prosidont, Mr. Warington W. 

 Smyth, iu the namo of the Geological Society, conferred upon Mr. 

 Poulett Scrope tlie highest honour at the disposal of that body, 

 namely, the Wollaston Gold Medal, in recognition of his researches 

 into the nature and origin of volcanos ; with which line of investi- 

 gation his name will always be indissolubly connected. 



II. — On the Subface-geology, Denudation, and "Form of the 

 Ground " of Belgium. 



By H. M. Jenkins, F.G.S., Secretary of the Eoyal Agricultural Society. 



THE review of my " Eeport on the Agriculture of Belgium," which 

 appeared in the last number of the Geological Magazine, 

 illustrated by a reprint of the map which originally accompanied it 

 in the " Jovirnal of the Eoyal Agricultural Society " (2nd series, vol. 

 vi., part 1), has induced me to offer some further remarks on the 

 surface-geology of that kingdom while the subject is still fresh in 

 the recollection of the readers of this Magazine. 



A mere glance at the map is sufficient to impress the geologist 

 with the remarkable parallelism existing between the boundary lines 

 of the surface-deposits and certain contour-lines, which show what 

 the late Professor Jukes delighted to call the " form of the ground." 

 The accompanying section, drawn from Ostend, on the north-west, 

 past Ghent, and through Nivelles, Namur, and Dinant, to near 

 Longwy, in the south-east, will illustrate my meaning. Ostend is 

 situated on the seaboard margin of a Polder-plain, the alluvial 

 deposits which constitute its environs having been reclaimed from 

 the sea chiefly within the historic period. Proceeding in a south- 

 easterly direction, the Polder alluvium is succeeded by a broad belt 

 of sand (the Gampine sands), which, although it appears almost a 

 plain to a casual observer, has in reality a slight inclination, so that 

 at about two-thirds of the distance across it we reach a height of 75 

 feet above the sea-level ; but, except in the Campine, at the extreme 

 east of Belgium, this sandy zone never attains a much greater 

 elevation. The perfect inclination of this zone is interrupted, and 

 its gradual rise is masked, by the valleys of several tributaries of the 

 Scheldt (Escaut), as well as by the wide and deep valley of that 

 river itself. 



South-east of the sandy zone we enter upon a broad belt of loam, 

 generally known as the Limon de Hesbaye, or Loess, and im- 

 mediately the gradient of the surface -incline increases to a very 

 remarkable extent. While previously the gradient has not been 

 more, and has generally been less, than 75 feet in 20 miles, or less 

 than three inches per mile, we now find the line of 150 feet elevation 

 running at a regular distance of about three miles from that of 75 

 feet, across two-thirds of the kingdom of Belgium. We have here, 

 therefore, the following noteworthy phenomena : — (1.) A gradient 



