Reports & Proceedings — Edinburgh Geological Society. 143 



geological evidence for subsidence has been overlooked by these 

 investigators, who paid no attention to the evidence afforded by 

 unconformable contacts or embayed shore-lines. 



The author feels that scientific opinion in regard to the origin of 

 coral reefs has been guided rather by subjective preference than by 

 objective logic. He considers that Darwin's theory of intermittent 

 subsidence is the most competent to explain the facts, and while he 

 holds that other theories than Darwin's deserve cordial consideration, 

 he feels that the burden of proof should be laid upon those who 

 assume that reef foundations have not subsided. 



II. — Edinburgh Geological Society. 

 January 16, 1918. — Professor Jehu, President, in the Chair. 



" The Supplies in Scotland of Felspars suitable for Industrial 

 Purposes." By Dr. Campbell. 



Eecent investigations of Scottish sources of alkali felspars had 

 been necessitated by (1) the difficulty of obtaining shipment of the 

 Scandinavian "spar", which is used extensively in the enamel, 

 glass, and pottery industries, and (2) the possibility of utilizing 

 potash felspars as a source of soluble potash salts, hitherto imported 

 from Germany, 



Dr. Campbell gave an account of the results so far obtained of an 

 inquiry carried out by Mr. Dinham and himself on behalf of the 

 Geological Survey of Scotland. Pegmatites, the chief source of 

 alkali felspars, were described from Beinn Ceannabeinne, the district 

 between Lochs Laxford and Inchard, llhiconich, and Overscaig in 

 Sutherlandsbire, from the Strontian district of Argyllshire, from 

 Portsoy, Banffshire, and from Monymusk, Aberdeenshire. It was 

 shown that, from their high content of silica and iron oxides, many 

 of the Scottish pegmatites would be classed as spar of Grade 3. 

 There were, however, abundant supplies of spar of Grade 2, and at 

 a few localities, particularly at Ehiconich, Strontian, and Mony- 

 musk, spar of Grade 1 (equal to the best Scandinavian spar) could 

 be made available by hand-picking. Analyses of the average material 

 of the best pegmatites gave potash content ranging from 7*42 to 

 9-35 per cent. The red potash spar at llhiconich was found to be 

 associated with a buif-coloured spar containing 7"13 per cent of soda, 

 which might be separated by hand-picking and utilized in the glass 

 industry. Estimates were given of the quantity of spar available at 

 each locality. The most extensive deposits are those at Beinn 

 Ceannabeinne, where at least 12,000,000 tons could be obtained by 

 open-cast working. 



Certain highly felspathic granites and felsites were regarded also 

 as likely to be of economic value. Of the granites examined, the 

 well-known Corrennie granite of Aberdeenshire was most promising. 

 An average sample of the rock yielded 8'02 per cent of potash, and 

 tlie only ferro-magnesian mineral present, biotite, occurs very 

 sparingly. The spoil heaps in the quarries would furnish an 

 immediate supply of many thousands of tons, and for practical 

 purposes the available supplies might be regarded as " unlimited ". 



