326 The Geology of Devizes. 
Figs, 4and 5.—Structure of Melbourn Rock and of Chalk Rock 
(magnified fifty times). 
but in it are scattered immense quantities of small round bodies 
which are either the cells of Foraminifera or of some allied organisms, 
Foraminifera are minute creatures which abound in all the seas and 
oceans of the present day, some living in shallow water, and some 
only in the open ocean. They extract carbonate of lime from the 
water, and construct tiny shells perforated by small holes, and these 
shells, either perfect or in fragments, have contributed largely to all 
parts of the Middle and Upper Chalk. A common form (Globi- 
gerina) is seen in the lower part of Fig. 6, and the small round 
bodies occurring in the surrounding material are nowhere so 
numerous and so robust as in this part of the Middle Chalk. The 
quarry below the butts on Roundway Hill is opened in this Chalk, 
and it forms the steepest part of the slopes round Oldbury Hill, 
Morgan’s Hill, and of the Downs that border the Vale of Pewsey. 
Chalk Rock. We now come to another well-marked horizon on 
the Chalk,and one that was first described from a section in Wiltshire, 
This is the Chalk Rock which has been worked for road metal in so 
many places on the Chalk hills, both to the north and south of 
Devizes. This rock is a hard white Limestone, lying in courses 
