54 LOWEB OOLITIC ROCKS OF ENGLAND : 
beare, and De la Beche.* Indeed, owing to the varying thickness 
and occasional disappearance of the Midford Sand, it is probable 
that the clayey conditions of the Lias endured longer in some 
localities than in others, f 
Upwards, the beds are closely connected with the Inferior 
Oolite, so that we are occasionally at a loss to say whether a 
particular layer should be assigned to that formation or to the 
Midford Sand. The upper junction is however more frequently 
exposed than the lower, for the latter is not often to be seen in 
section, although its position is fairly well-marked by springs 
thrown out by the Upper Lias clay. 
The thickness of the Midford Sand is subject to much 
variation, for in the neighbourhood of Bath and the Mendip 
Hills the beds occasionally taper away. In the Cotteswold area 
the beds are from 10 to 120 feet thick ; in Somersetshire they 
attain a maximum of 200 feet ; and in Dorsetshire 150 feet or 
more. 
These beds, as previously stated, include generally the zones of 
Ammonites opalinus and A. jurensis. In many places however 
they are comparatively unfossilferous. The observations of Mr. 
Buckman (to which reference has already been made, p. 40) show 
that in different areas the mass of the sands may be assigned 
palaeontologically more to one than to the other of these zones, 
and that portions of the Upper Lias shale of Dorsetshire may 
belong to the zone of A. jurensis. 
In Dorsetshire the beds are often spoken of as the Yeovil and 
Bridport Sands. 
Bridport (Coast Sections} to Beaminster. 
On the coast at Bridport the Midford Sand is well-exposed in 
the cliff-sections, and it comprises a series of yellow sands with 
nodular layers and bands of calcareous sandstone. (See Fig. 33.) 
In proceeding eastwards from Golden Cap, the first exposure 
is at Thorncombe Beacon, where beneath the Upper Greensand 
and possible traces of Gault, there occur about 100 feet of yellow 
sands that exhibit a gradual passage into the Upper Lias shale 
beneath. The beds, however, can only be contemplated at a dis- 
tance, for the higher portions of Thorncombe Beacon are not 
accessible. 
Immediately west of Bridport Harbour there is a low cliff, 
about 40 feet high, showing yellow sand, with three or four bands 
of calcareous sandstone, having a slight inland dip. Small caves 
have been hollowed out in the beds, along lines of weakness, that 
were produced no doubt by a fault that brings the beds abruptly 
against the Fuller's Earth. This fault runs somewhat obliquely 
* Trans. Geol. Soc., ser. 2, vol. i. p. 306, and vol. iv. p. 31. 
f See H. B. W., Geol. Mag., 1872, p. 513. 
