PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 25 
The other associates of the Haughtonite are here oligoclase and magnetite. 
The crystalline plates are here generally of only an inch or so in size ; 
occasionally, however, they are much larger. They are of a deep black colour. 
All other characters and reactions agree with those of the Roneval mineral. 
The specific gravity is 2° 99. } 
1°3 grammes gave— 
Silica, ‘ : : "457 
From Alumina, ; *028 
“475 = .86°538 
Alumina, . ; , 4+ 22.8282 
Ferric Oxide, . : 5 OAS 
Ferrous Oxide, . : s 16009 
Manganous Oxide, . i "784 
Lime, : : : » 1°249 
Magnesia, . : . LOF 
Potash. : : eo abe: 
Soda, ‘ : : 794 
Water, : : syarite 506 
99° 856 
Insoluble silica, 3:791 per cent. Possible impurity, oligoclase. 
From Micaceous Gneiss. 
6. The gneiss of the hill of Clach-an-Eoin (Yone), situated between the 
mouths of the Navir and the Borgie, in Sutherland, exhibits on its glaciated 
front a peculiarity of structure which I have not seen described. In feeble, 
comparatively very feeble development, something of the same kind is to be 
seen in the gneiss of Boggierow quarry near Portsoy,—at Strath Virick Bridge, 
near Arguish,—and at Innisbae, on the Dirrymore road in Ross-shire. 
At the first, and possibly also at the second of these localities, the structure 
may be regarded as a mere modification, or a badly-developed instance of 
porphyritic arrangement in the felspathic portion of the stone. At Boggierow 
the crystals of the felspar, if crystals they be, are devoid of all edges and 
angles, appearing rather as kernels or nodules, of some half inch or so in size. 
Of these there is here no definite arrangement whatever,—they are pro- 
miscuously scattered throughout the mass. 
As regards the size and want of angularity of the felspathic portions of the 
Innisbae rock, the above also holds ; but there is here no promiscuous scattering 
—no absence of arrangement. These felspathic kernels lie in regular layers 
VOL. XXIX. PART I. G 
