TRANSACTIONS OF SECTION C. 051 



but exclusively of quartz, quartzite, veiu quartz, and chert, show unmistakable 

 eviflence of sand-blast action. 



' Pyramidal pebbles ' are common, with surfaces showing different degrees of 

 polishing. Some of them even present strongly concave surfaces and finer depres- 

 sions beautifully polished. A considerable number show ' flaking ' of their edges, 

 and the surfaces so formed have subsequently been subjected to different degrees of 

 polishing. The cherts are beautifully fretted, and exhibit in perfection the results 

 of difl'ereutial etching. 



Inquiries as to definite orientation of the more polished surfaces of the pebbles 

 have hitherto failed to yield results. The author believes that no such definite 

 orientation obtains, and is of opinion that the pebbles had been subjected to con- 

 tinued sand-blast action in some other locality, and were suddenly and forcibly 

 transferred by the action of water to their present position, where many of them 

 were again subjected to further sand-blast action. 



The result of the examination of the pebbles supports the author's contention, 

 based on this microscopical characters of their constituent sand-grains, that the 

 Cutties Hillock sandstones are really Triassic sand-dunes. Other reasons for 

 arriving at the same conclusion are : the peculiar undulating bedding of the sand- 

 stones, differences in the mode of occurrence as well as ontological differences of 

 the fossils from what obtain in the adjoining areas. 



In the case of the other local Triassic areas deposition in water is assumed, 

 though the debris had evidently in some cases for a long time previously been sub- 

 jected to wind action on a land surface. 



5. The Occiirrence of Covellite in Associaiioib tcith Malachite in the Sand' 

 stone of KbujBtejis, Nairn. ByW. Mackie, if.yl., if..Z). 



In a vein or lissure of about IJ inch width in Kingsteps Quariy, Nairn, the 

 sandstone is found to be impregnated with copper ore. The vein shows an indigo 

 coloured centre of about J- inch in width bordered by green margins of about 

 the same dimension. Analyses of the different parts gave results which show 

 that the copper ore exists in the centre of the vein, chiefly in the form of the 

 monosulphide (CuS) ana mostly in the form of malachite at the margins. The 

 former, which is the mineral covellite, is apparently new to Scotland, as no mention 

 is made of it in Ileddle's ' Mineralogy of Scotland.' Nairnshire must also be 

 recorded as a new locality for malachite. 



G. The Source of the AJlnvial Gold of the Kildonan Field, Sutherland. 

 By J. Malcolm Maclaren, B.Sc. 



In this field gold is practically confined to the small area drained by the 

 Kildonan, Suisgill, and Kinbrace streams, all tributaries of the Ullie or Helms- 

 dale. The . rocks of this area are granites and quartz-, flaser mica-, and granulitic 

 biotite-schists. The lines of demarcation between the various schists are at all 

 times diflicult to trace, since the whole countryside is covered with a thick 

 deposit of the Glacial Drift. Fine flakes of gold have been found in many places 

 in the Glacial Drift, supporting the inference that alluvial gold is more or less 

 dispersed throughout. It is only in alluvium resulting from the action of the 

 present watercourses that concentration of the Drift has been carried to such an 

 extent as to attract commercial attention. The gold itself is found in nuggets 

 and scales, the largest of the former weighing 2 oz. 17 grains. The .scales pre- 

 sent little evidence of rounding due to attrition or rolling friction. Veins of 

 'clean' quartz have been found in the upper waters of the Kildonan. One of 

 these veins on analysis yielded gold. The writer concludes that the alluvial 

 gold has been derived from the white quartz veins of the local schists (which are 

 almost certainly metamorphosed sediments, possibly originally containing alluvial 

 gold). The ecnists were crossed by glaciers travelling in a general south-easterly 



