298 The American Geologist. May, 1897 
the waves. A prolonged search failed to discover any layers 
containing fossils suHlciently perfect for identification. Of 
the fragments obtained, only a few were in such condition as 
to warrant specific determination, and these were species 
which might be found either in Recent, Quaternary or even 
late Tertiary beds. Hence it has not been possible to deter- 
mine the exact age of this bed, the oldest of the Bermuda rocks. 
Unconformity at the Top of the Base Bock. This layer of 
base rock outcrops at various places along the south shore, 
and reaches different elevations, according to the amount of 
erosion of the sea and the consequent stripping off of the 
overlying teolian rocks. As has been stated, the base rock is 
often absent. The marked difference in compactness between 
it and the seolian beds above, has permitted the development 
of extensive clili['s, with the foot resting on the base or beach 
rock. Where this base rests well above the sea level, .the base 
rock projects in the form of rugged points and slopes, while 
where its contact is near the line of wave attack, the soft over- 
lying rocks, undermined at the contact, are maintained in the 
form of overhanging cliffs. Hence the difference in rock tex- 
ture is often brought out into striking relief in the topogra- 
phy of the shore line. 
While it seems evident that the base rock must ever3^where 
underlie the seolian beds, positive proof of this is absent. This 
admits of either one of two interpretations: — first, that the 
dense lower rock is local, and has no special significance, as 
some of the previous observers have thought, or second, that 
the surface of the beach rock is irregular, because of erosion 
before the blown sand was made to cover it. Other observa- 
tions described below prove the latter to be tiie correct inter- 
pretation. 
At various places along the south, shore, but notably on the 
northern side of Devon bay, the surface of the base rock is 
seen to be distinctly that of an eroded rock surface. Whether 
the denudation which produced this irregularity is that of land 
or sea is not apparent; but the absence of a soil at the top, and 
the presence of pebbly beach deposits over the surface, shows 
that in some places the waves were at least the last to work. 
More convincing evidence of a distinct unconformity and 
erosion surface is present in the form of a conglomerate beach 
