380 THE CRETACEOUS ROCKS OF BRITAIN. 
massively bedded white chalk of the Terebratulina zone. In the 
upper part of the latter zone well marked layers of marl occur, like 
those at Dover, though the seams do not all appear to be at the 
same horizon ; flints also occur either as scattered nodules or in 
widely separated layers. In the highest part of the Terebratulina 
zone hard crystalline lumps occur, which frequently show the 
structure of Ventriculites or other sponges in'iron stains. 
Although many borings have been made through the Chalk of 
Kent, in no case have the well sinkers preserved a sufficient record 
of the characters of the different beds traversed to enable us to 
recognise with certainty the top and bottom of the Middle Chalk ; 
but it is probably over 200 feet thick, and if a boring at Sitting- 
bourne recorded by Mr. W. Whitaker is correctly interpreted, it 
is there about 221 feet thick.* 
The following is a brief account of the more important of the 
exposures seen along the outcrop of the Middle Chalk through 
Kent. 
Stratigraphical Details. 
All the following information was obtained by Mr. W. Hill, 
during a rapid survey of the outcrop in 1897. He did not visit 
such quarries and exposures as exist between Folkestone and Bra- 
bourne, as these are not likely to differ from the corresponding 
portions of the coast section, but took up the inland outcrop near 
Brabourne and the valley of the Wye. 
The Melbourn Bock is not infrequently exposed along the base 
of the North Downs, but the upper part of the zone of Rhynch. 
Cuvieri is seldom seen. Nearly all the quarries which have been 
opened on the slope of the Downs between the Valley of the Wye 
and the western border of Kent are worked in the soft white chalk 
of the Terebratulina zone. Many are very large, but the chalk 
seems now to be used only in small quantities to make lime for 
local purposes. The chalk is massively bedded, featureless, and 
almost unfossiliferous, so that, although the quarries often exhibit 
fine sections, they are as a whole uninteresting. 
Hard, rough nodular chalk with Rhynchonella Cuvieri can be 
seen in the field-way'over the Downs from Newgate Scrubbs, east 
of Brabourne and a large quarry on Brabourne Down is opened in 
the lower part of the Terebratulina zone. 
In the valley of the Wye a small quarry by the roadside, 330 
yards north of the main entrance to Olantigh Towers, exposes 
hard rough chalk which is probably the top of the Melbourn Bock. 
Similar rock is seen again in a quarry 300 yards south of All Saints 
Church, at Boughton Court (see p. 48) ; and on White Hill, half 
a mile north of Boughton Corner, is a large quarry in the upper 
part of the Terebratulina zone. The chalk exposed here includes two 
marly layers and a bed with hard lumps or masses showing the 
structure of sponges in iron stains ; many large flints are also seen. 
* The Rochester Naturalist, Vol. iii., p. 60 (1901). 
