530 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 24, 



The tract is known by the name of the Windyhills, and is situated 

 close beside the hamlet of Woodhead, in the neighbourhood of the 

 River Ythan. The whole crest of the ridge is thickly covered with 

 great sheets of quartz-pebbles, mixed with a fine whitish sand derived 

 from the grinding down of the fragments. These pebbles are of all 

 sizes below that of an egg, for the most part a good deal smaller. It 

 is true that bigger pieces occur ; but there are no large boulders. 

 Several holes or excavations show the mass to be very homogeneous 

 and remarkably devoid of any foreign fragments. A few coarse 

 water-worn flints occur, generally of large size — often nearly six inches 

 in diameter, and frequently with a white chalk-like exterior. I did 

 not find any trace of shells or other fossils in those I picked up. 

 They are for the most part of a very coarse quartzy character, and 

 are whitish, blackish-blue, or yellowish in colour, and are generally 

 unlike the flints of the ridge previously described. 



The peculiar significance of this gravel (which covers a tract about 

 two miles long and a mile broad) lies in the fact that it is not a drift- 

 gravel, but an accumulation of local origin, derived from the quartz- 

 beds of the clay-slate strata on which it rests. The pebbles are not 

 pure quartz, but contain a considerable proportion of felspar, whose 

 decay gives to the mass a particularly white aspect. 



Thinking it of some importance to determine the precise height of 

 this ridge, I levelled it from a point of known elevation in the imme- 

 diate neighbourhood, and found the summit to be 412 feet above the 

 mean level of the sea. 



No clay was found overlapping this deposit ; nothing covers it but 

 some peat-moss. I should say that it had formed a shoal or bank 

 covered by very shallow water, the lashing of which had ground 

 down the quartz into the shingle that we now see. Had the water 

 been of any depth, there would have occasionally occurred seams of 

 clay or fine sand interstratified with the pebbles ; but such is not the 

 case. 



No transitory flood can account for these extensive shingle-banks ; 

 a lengthened period of time is demanded for grinding down the hard 

 quartzy fragments into their present smoothly-rounded form. The 

 thick accumulations of finely-laminated silt which line the lower part 

 of the Spey valley and margin the surrounding coast, the evidence 

 of the molluscs found imbedded in their native mud, together with 

 the silent testimony of these gravelly shoals, all converge to prove 

 that the sea-waters had long stood over this part of Scotland some 

 450 feet higher than the present coast-line. 



On the emergence of the land from the waters of this Pleistocene 

 sea, I find evidence that the country had attained a greater elevation 

 than it does at present. This is shown by superficial beds of peat 

 passing down below the present sea-margin. 



In the links, or low sandy flats, adjoining the beach at Aberdeen, 

 I have seen peat beneath the surface of the sea-sand ; and at the 

 mouth of a small rivulet, which divides the parishes of Belhelvie 

 and Foveran, I have observed a formation of peat passing directly 

 under the sea-beach. 



