Transactions. 177 



hundred pieces of granite in the search, but have been equally 

 unsuccessful. There can be little doubt, I think, that crystals of 

 Sphene, which are found in this granite, have been mistaken for it 

 by careless observers, as some of the Sphene crystals, superficially 

 looked at, somewhat resemble Zircon in colour and form ; I think, 

 too, that broken pieces of Psilomelane must have been mistaken 

 for Antimonite, at Kinharvy, although there is little resemblance 

 between these two minerals. Although I never found Zircon in the 

 Criffel granite, my friend, Professor Heddle, and I were fortunate 

 enough to find Alleuite in it ; this mineral is sparingly found in 

 some of the granites in the north of Scotland. We also found in 

 this granite, for the first time in Britain, the rare mineral 

 Gadolonite ; it exists very sparingly ; since then we again found 

 this mineral in the granite from Ben Loyal, Sutherlandshire. I 

 may just allude to an instance showing the importance of being 

 able to recognise granites from their enclosed minerals. A gentle- 

 man who was engaged in the investigation of the drift beds and 

 boulder clays in the north-west of England and North Wales 

 wrote to me that he and Professor Bonney had a strong impression 

 that many of the boulders in these drift beds had come from the 

 south of Scotland, and asked me if I thought I could identify any 

 of the granites and rocks from this neighbourhood. I wrote to him 

 I should be glad to assist him. He sent me a large number of 

 rock specimens from the drift and boulder clays in the neighbour- 

 hood of Liverpool and North Wales. I found I could say with a 

 great degree of confidence that many of the granites and rocks sent 

 were from this district, as I found crystals of Sphene in them, 

 and I was quite certain that this was the case when I found, by 

 great good fortune, a crystal of Allenite in one of the pieces of 

 granite. It was more than a thousand chances to one finding this 

 crystal of Allenite, as it is rather a rare mineral to find in our 

 granite, even when carefully looked for.* I have never found 

 Sphene in the granite of Cairnsmore, but fiiir specimens of Epidote 

 are to be got in the granite quarry near Creetown, and in some 

 other localities — generally poor. Amethyst and Smoky Quartz 

 (Cairngorm) are found on Crifi"el and a few other localities. The 

 former is very abundant on the west side of Criffel, above South- 

 wick House ; more sparingly near Dalbeattie. Clear crystals of 

 Amethyst, suitable for jewellers' purposes, are rarely found ; I have 



* " Quarterly Journal of the Geological Society " for May, 1883, p. 119. 



