1868.] TOPLEY BAS-BOULONNAIS. 473 



in Kent. 'J he Lower Greensand is too thin to make a constant 

 feature in the district ; towards the south and south-east, however, it, 

 together with the underlying ferruginous sands, forms the range of 

 hills which runs more or less parallel with the Chalk, but without 

 making a well defined escarpment. The hills of the central district, 

 which are capped by ferruginous sands (Wealden), are mostly 

 barren. 



II. Description of the Beds. 



1. Upper Greensand and Gault. — These beds differ but little from 

 those seen on the Kentish coast, and have been so often described 

 that I will only note the section exposed (in June 1866) in the new 

 railway-cutting at Caifiers. 



Chalk-marl. 



Chalk-marl, with green grains, sandy and con- 1 o ^^ S feet 



taining nodules in the lower part J 



Gi'eensand with phosjjhatic nodules passing 1 4 ^.^ p 'nohes 



into very green clayey sand J 



Blue Clay (Gault). 



The Gault is much thinner in the Boulonnais than in Kent, probably 

 not more than 50 feet at Wissant. It has the same character m 

 both places, and does not need detailed description. 



2. Jimction Beds. — The layer of phosphatic nodules so characteristic 

 of the base of the Gault in the south-east of England is also equally 

 well shown in the Boulonnais. 



At Copt Point this bed is very wellseen along the cliff below the 

 dark Gault clay. It is about 1 foot thick, mostly composed of 

 phosphatic nodules and pyrites in a state of decomposition when 

 exposed to the air. Wood bored by moUusks is also common. The 

 fossils found in this bed are seldom entire, often in casts, and aU 

 pliospliatic. Below this comes loose quartzose sands, also containing 

 phosphatic nodules and fossils. This sand is of varying thickness ; 

 it rests upon, and sometimes passes into, a rather coarse, hard, cal- 

 careous sandstone. 



This account will exactly describe the junction at Wissant cliffs. 

 The phosphatic bed containing much wood may here be very well seen 

 under the Gault, and overlying the calcareous sandstone, which stands 

 out in rocks at low water. 



Fig. 1. — Section in Railivay -cutting luest of Gaffiers, 



a. Angular flint-gravel 



b. Blue clay (Gault) 



At Caffiers cutting the junction was very distinctly seen, and gave 

 the above section (see fig. ^ ). 



