Tertiary Gravels in Aberdeenshire. 223 
character, but often extraordinarily like the clays that accompany 
the pebbles at Windyhills and Delgaty. On the surface with these 
pebbles occur fragments of slate, knotted schist, pebbly grit, granite, 
norite, hornfels, and other rocks of local derivation. 
Unfortunately, the few natural exposures are very unsatisfactory 
and there are no pits at present being worked, as these pebbles are 
not used for road metal except on the farm roads. Consequently 
it is very difficult to obtain an exact idea of the composition and 
structure of the beds and their relations to the glacial and 
metamorphic rocks. 
At the east end of the Corse of Balloch the peat gets thinner 
and cultivation encroaches on the area of gravel. At Hillside of 
Aldie traces of many shallow pits are visible. They are now nearly 
filled up, but we were told that they were sunkin search of a whitish 
clay which it was thought might be of value. Samples were 
examined, but it was reported that the material was not of economic 
value, though when the clay was washed it was possible to make 
clay pipes from it. Some of these pits are said to have been 10 to 
12 feet deep in the gravel without reaching the subjacent rock. 
The whole surface of the ground is covered with rounded flints and _ 
quartzites, while pebbles of metamorphic rocks, deeply weathered, 
are numerous. We dug for about 3 feet into the gravel, and after 
a foot or so of peaty soil with iron pan, we reached, apparently 
undisturbed flint gravel embedded in yellow and whitish clayey 
sand. The pebbles were all very well rounded flint and quartzite ; 
the flint had a thick white weathered crust, and when split open 
presented a waxy rotten appearance, like the flints at Windyhills. 
At North Aldie it was possible to lay down the margin of the 
outlier with fair definiteness at 300 feet. Below. that the pebbles 
were frequent in the soil, but were obviously transported down the 
slope. The deposit seemed to rest directly on the granite, which is 
here the country rock. 
On the hill-top a mile er so further east, near Newton and Mount- 
pleasant, the same phenomena are repeated. The lower slopes are 
granite and red boulder-clay, with mounds of glacial gravel and 
sand. As the 300-ft. contour is approached pebbles of flint and 
quartzite become very numerous in the fields, and above that level 
we pass suddenly on to beds of solid flint gravel capping the hill- 
’ tops. The field exposures indicate that this gravel has a nearly 
horizontal base resting upon a platform of granite, which shows 
minor irregularities in the form of low granite ridges emerging 
through the gravels. At least 90 per cent of the pebbles are flints 
from 2 to 7 inches in diameter, very well rounded, and deeply 
weathered. Pebbles a foot long are rare. Pure white quartzite 
pebbles are always present, though only in subordinate amount, 
and there are also local granite and schist pebbles. No strati- 
fication is visible. Large erratics of granite occur scattered over the 
ground, but we saw no section which established the relations 
