650 REroKT— 1901. 



It occurs mainly in nodules -which range in size from a hazel to a walnut dis- 

 seminated through au extensive mass of sandstone along tlie coast of Elginshire, 

 near Covesea Lighthouse, where iu consequence of its iuiiueuce on the weathering 

 of the sandstones some unique results in rock sculpturing have been produced. 

 Analyses of some of these nodules show that they contain as much as 37 per cent, 

 of barium sulphate. In the nodules the barium sulphate is shown by the micro- 

 scope to directly envelope the i^rains of sand, except toward the peripliery where 

 rims of secondary quartz and ferric hydroxide come between the sulphate and the 

 original grains. 



The presence of calcium fluoride iu rochs of the same age at Cummingston a 

 little further to the west than the barium sulphate area was also determined by 

 the author iu 1895. The fluoride occurs in small white, often square-shaped, 

 patches, showing lustre-mottling disseminated through the mass of the sandstone. 

 Sometimes it occurs in aggregates which on section show that they are made up 

 of cubes placed in juxtaposition. There are also occasional bands cemented 

 throughout by calcium fluoride, but oven in these lustre-mottling shows that it 

 occurs in masses of closely placed cubes. The presence of fluoride was determined 

 by obtaining a copious precipitate of gelatinous silica on heating the powdered 

 sandstone with strong sulphuric acid and passing the evolved gas into water. As 

 much as 25'S8 per cent, of calcium fluoride was obtained by analysing an average 

 specimen of the sandstone in detail. The microscope shows the presence of a 

 colourless isotropic substance directly enveloping the sand grains. Towards the 

 periphery, as in the case of the barium sulphate nodules, secondary quartz rims 

 and fei-ric hydroxide are occasionally seen to come between the fluoride and the 

 original grains. 



The author disputes the explanation of Professor Clowes as regards the 

 raison d'etre, of the barium sulphate, the presence of which has been ascribed by him 

 to the double decomposition of barium chloride — which he finds present in some 

 of the local deep well waters — by the soluble sulphates of the infiltrating waters. 

 On the contrary, the presence of both barium sulphate and calcium fluoride is 

 ascribed to the concentration of the waters of an inland lake from which these 

 substances if present — and both of them are present in sea water — would naturally 

 be deposited in the order of their insolubility as concentration went on. The 

 presence of beds of common salt iu the English Trias presupposes the existence of 

 such a salt-impregnated lake over the southern area, and the same conditions may 

 be reasonably extended to the Elgin area during the same geological period. 



4. The Pebble-band of the Elgin Trias and its Wind-u'orn Pebbles. 

 By Wm. Mackik, M.A., M.D. 



The Cutties Hillock pebble-band, which has figured so largely in the discussion 

 of the succession of the Elgin sandstones, is not, as has generally been contended, 

 a pure localism. Two new openings into the Triassic rocks of the area show that 

 it is present at five widely separated points. Its characters are constant in all. 

 There is evidence that it is basal in position in the Triassic formation, and taking 

 it as a datum line one is enabled to fix the relation of the Triassic to the under- 

 lying U.O.R. rocks with some certainty. It shows that the former overlie the 

 truncated edges of the latter beds in a thin cake, which is proba1)ly nowhere more 

 than 100 feet in thickness on a surface slightly inclined upwards from the south- 

 east to the north-west, while the U.O.R. rocks steadily dip at almost constant 

 angles in the opposite direction. Other facts definitely ascertained are, that the 

 two series of rocks wherever they occur in proximity invariably show marked 

 discordance of dip and strike, and that the Cutties Hillock area is detached from 

 the other local areas of Triassic rocks, U.O.R. rocks having been traced all round 

 it, and quite a mile intervening between it and the Spynie and Findrassie area to 

 the noi-th-west, in which interval U.O.R. rocks with discordant dip and strike 

 also appear. 



Another interest attaches to the pebble-band in that its pebbles, which are all 



