118 • REPORT 1859. 



district it becomes attenuated to a very narrow zone. In the Glenshee and Stone- 

 haven sections the mica-slate appears to lie below the gneiss, and not over it, as 

 usually represented. There are great tracts of mica-slate also in the north-west, 

 between the Spey and the Deveron, where it is intermixed with gneiss and clay- 

 slate, but the relations of the deposits are little understood. It often contains 

 garnets, more rarely Andalusite, and some other minerals. 



Clay-slate also covers a considerable space in this district, chiefly to the south of 

 Banfl'and the Troup Head. It is quarried in several places for roofing-slates, as near 

 the Troup Head, in the Foudland Hills, and near Gartly. These slates are wrought 

 on lines of cleavage, the bedding being in general scarcely perceptible. It has been 

 said that fossils — graptolites — occur in this rock ; but there is no foundation for this 

 statement. I formerly described these clay-slates as probably Silurian ; but this is 

 only a theory, and as the clay-slate in the Southern Grampians appears to dip north 

 below the mica-slate, this view now requires confirmation. In Glenshee a curious 

 Beries of black carbonaceous slates, containing graphite like those of Easdale, occur. 

 Graphite is also found in other parts of this region, in the metamorphic strata — a 

 most important fact in reference to the theory of these rocks. 



The Old Red Sandstone chiefly occurs on the outskirts of the region we are con- 

 sidering. The principal mass within it runs south from Gamrie — a locality well 

 known for its nodules with fossil fish. Another isolated, but interesting portion 

 occurs round the ancient Castle of Kildrmnmy, in which impressions of plants have 

 been found. A curious mass of conglomerate at the Old Bridge of Don probably 

 belongs to the same deposit. On the southern limit of the map, the Great Red 

 Sandstone formation of Strathmore begins, and is well seen in huge beds of red 

 sandstone and conglomerate near Dunnottar. The conglomerate must be regarded 

 as marking rather the shore-lines, or certain peculiar local conditions, than any 

 particular zone in the formation. 



At the other extremity of the map on the Spey, the Morayshire deposits begin 

 with numerous fishes at Tynet Bum, Dipple, &c. " Still further west are the beds 

 with reptilian remains at Elgin, probably in the upper Old Red, or some newer 

 formation, but beyond the limits of this paper. 



Higher deposits are only known in fragments. Such is the portion of lias near 

 Turriff, perhaps in situ ; but other masses of clay with lias fossils, as pear Banff, are 

 more probably drifted. So also the greensand and chalk flints, spread over the rising 

 ground from Peterhead to Cruden — noticed and collected in 1834 by the late Dr. 

 Knioht of this University — are apparently detrital masses. Their number, however, 

 and state of preservation show that strata of this age probably once existed here in 

 situ, and perhaps they may still occur below the waters of the North Sea. I 

 formerly noticed the analogy of these deposits to those in the south of Sweden, 

 where lias rests on gneiss, and is covered by chalk ; but Flamborongh Head is the 

 nearest point where the chalk is now known in situ. 



Last of all are the great detrital masses of the Drift or Bouldcr-clay. This forms 

 two very marked divisions, evidently formed under very opposite conditions of the 

 land. 1st. The lower boulder-clay composed of thick beds of Ann brown or grey 

 clay and fidl of large striated stones, some of them several feet or yards in diameter, 

 and evidently deposited in an arctic sea round the shores of an ice-clad land rapidly 

 sinking in the waters. Glaciers, as the striae they have left on the rocks testify, 

 must then have covered our mountains, and floating icebergs filled our ocean. 

 Above this deposit are : — 2nd. Loose, distinctly stratified sands and gravels with 

 rounded water-worn stones. These are clearly a portion of the lower masses recon- 

 structed as the land, now freed from ice, rose gradually above the waters. The 

 brick clays, some blue, some red, are again only the finer materials washed out in 

 this process, and laid down in gulfs and bays and the quieter parts of the sea along 

 the coast. They contain arctic shells — showing that the climate was still cold ; 

 and also at Clay-hills, in the very city, star-fish (Ophiura), bones of fish like the 

 cod or haddock ; and full 30 feet below the present surface bones of a small duck. 

 They are well seen at Belhelvie, Old Aberdeen, and Tome, but occur in many other 

 localities. All along the south coast too, the fishermen dredge up, attached to the 

 large mussel by its byssus, valves of the Pecten islandims and the small Leda dblonga, 

 shown by their colour to have been imbedded in similar red clays. 



In the peat-bogs we have remains of even a more recent period, but little anterior 



