118 
SILUEIA. 
[Chap. VI. 
d\ have been extracted, leaving only a few arches for support ; whilst the 
other beds, consisting of impure and nodular earthy limestone with much 
Section across the Wken's Nest. 
(From Sil. Syst. p. 484.) 
dK Lowest Wenlock shale (place of Woolhope limestone ?). d 2 . Wenlock shale. 
d 3 . Two bands of limestone separated from each other by ' bavin,' e. They are 
represented by the white spaces, from which the best limestone has been quarried, 
leaving only arches of support. e*. Overlying ' bavin ' or shale, passing up into 
Ludlow rocks. 
shale, locally called ' bavin,' thus form the framework of the hill. The 
dotted arch indicates what the dome might have been, probably never entire, 
whilst the tinted portion of the drawing represents the body of the hill, 
the upper surface of which, having been hollowed out towards the centre, 
has obtained for it the name of Wren's Nest. It is therefore an elevated 
dome, which may have been produced by lateral pressure, and was probably 
truncated at its summit during the same period of disturbance and denu- 
dation which gave to the mass its peculiar form. 
"When viewed from below on its southern face, and where necessarily 
the excavated depression on the summit cannot be seen, the flank of the 
dome of shale or ' bavin,' whence the limestone has been entirely removed, 
presents the appearance shown in this sketch. 
The South End of the Wren's Nest. 
(From a Sketch by the late Eev. W. Whewell, D.D. Sil. Syst. p. 485.) 
The spectator, looking to the north, sees how the limestone strata fold over a central 
dome of shale. 
