Tertiary Gravels in Aberdeenshire, 221 
surface of the outlier, and at its edges, especially on the north side, 
it seems to be overlapped by a thin skin of boulder-clay, but no good 
section proving this was observed. The evidence led us rather to 
believe that, like many of the adjacent hill-tops, Windyhills rises 
through the general spread of drift which mantles all the lower 
ground ; the pre-glacial rocks thereby emerge at the surface. 
From a consideration of the evidence detailed above, certain 
conclusions seem to be reasonably clear. 
The Delgaty and Windyhills deposits exhibit peculiarities which 
demonstrate that they are essentially the same. They are parts of 
a deposit once probably continuous, the relics of an extensive sheet 
of gravels, sands, and clays, now almost wholly removed by 
denudation. Itis very significant that they both occur at elevations 
of 360-400 feet ; possibly they rest on an old platform, at any rate, 
they indicate submergence. It seems impossible to believe that they 
are stream gravels, as this would involve the former existence of 
a river system, of which no other traces can now be found. Almost 
certainly they are marine, and point to a general depression of this 
part of Scotland amounting to at least 400 feet. 
As regards their age, only two points are certain. They are post- 
Cretaceous because they contain flints with chalk -fossils; they 
are pre-glacial because they are covered by a boulder-clay which is, 
so far as we know, the earliest glacial deposit of the district. It 
seems safe, accordingly, to regard them as Tertiary. 
All the available evidence points to the conclusion that these 
gravels are in situ, and almost undisturbed. No boulder-clay has 
been found beneath them, and the field evidence indicates that they 
rest immediately upon a platform of the older rocks. No veins of 
boulder-clay can be seen in the pits. We know of many large erratics 
that have been transported by ice without having their stratification 
greatly disturbed. But the nature and size of these gravel masses, 
their composition, the freedom from contortion, veining or inter- 
calations of boulder-clay, and, above all, their remarkably uniform 
elevation above sea-level, point unmistakably to their interpretation 
as pre-glacial accumulations. The ice in this part of Aberdeenshire 
was perhaps comparatively thin and moved slowly. In many places 
the rotten rock below the boulder-clay shows that locally the ice 
had little excavating power. Many of the peculiar quartzite pebbles 
of Windyhills type are found in the glacial deposits, and show 
that much destruction of these beds took place; what remains is 
probably only a fragment which has escaped erosion. 
GRAVELS OF THE BucHAN RIDGE. 
About 15 miles east of Windyhills there is a low flat-backed 
ridge that runs in an east-north-east direction from Whitestone 
Hill (530 feet) and Dudwick Hill (572 feet) to Stirling Hill and Buchan 
Ness (see Fig. 2). The flint gravels of this Buchan Ridge are very 
