IN GLEN TILT. 3 It 



containing specks of felspar, or small cavities, which may be 

 supposed to have been once filled by it. 



35. I return now to a farther consideration of the rocks 

 along the bed of the river, which consist partly of strata, and 

 partly of sienite. Our examination of these, and indeed of the 

 whole Glen, was much facilitated by the kind hospitality of 

 the Duke of Atholl, who allowed us to fix our residence at Fo- 

 rest Lodge for several days. 



36. Among the substances that compose the strata, gneiss, 

 hornblende-slate, granular quartz, and granular limestone, have 

 already been mentioned. Mica-slate occurs more rarely. Be- 

 sides these, there are many compounds of quartz, felspar, mi- 

 ca, hornblende, actinolite, compact dolomite *, chlorite, talc, 

 steatite, and serpentine, which, in different rocks, are found in- 

 timately mixed in a great variety of combinations, and in diffe- 

 rent proportions. As examples of these compounds, I may 

 mention that, among the specimens we collected, one is a com- 

 pact dolomite, penetrated by chlorite and talc ; a second, horn- 

 blende-slate, penetrated by carbonate of lime ; a third consists 

 of actinolite, felspar, mica, and carbonate of lime ; a fourth, of 

 felspar, with hornblende and carbonate of lime; a fifth, of 

 quartz, compact dolomite, and brown felspar; a sixth, of 

 quartz, penetrated with chlorite, talc, and carbonate of lime ; 

 aud other varieties might be added. We found steatite and 



Vol. VII. P. II. S s serpentine 



* By Compact Dolomite, I mean a magnesian limestone, differing from com- 

 mon dolomite, in having its structure compact, and such as to render the frac- 

 ture not granular, as in common dolomite, but splintery, and passing to the 

 even. The fracture is thus well described by Mr Jameson, in his account of the 

 dolomite of I-columb-kill, in his Mineralogy of the Scottish Isles ; and the name 

 of Compact Dolomite has been used by the Comte de Bournon, in describing 

 some specimens from that island, in the collection of Mr Allan. Compact dolo- 

 mite is found also in GlenElg, and in Kintail, on the coast opposite to the island 

 of Skye. 



