160^ Pro§€§dings of PhilofopMcal Societies, ^Avo | 



serpentine is vertical and is well characterized. It contains in. 

 part veins of asbestos, and in parts diallage, and a large mass of 

 nypersthene. 



On the other side of this dyke of serpentine, which is 90 yards 

 thick, fine grained sandstone and conglomerate again appear 

 and dip away from the serpentine towards the S. Next to these 

 a mass of serpentine is seen mixed with dolomite, and at its side 

 altered sandstone and a conglomerate in which the quartz peb- 

 bles are split and re-united by ferruginous matter. Lastly, at a 

 short distance a dyke of greenstone parallel to the serpentine 

 occurs flanked on both sides by vertical masses of sandstone 

 and conglomerate much altered and indurated, and charged with 

 brown spar. 



Mr. Lyell next describes the rocks on the right bank of the 

 river, which resemble those on the left with one exception, viz. 

 that the great dyke of serpentine seems to be connected with the 

 mass of dolomitic serpentine, a thin bed of fine grained green- 

 stone alone intervening, and the sandstone and conglomerate 

 which appeared between them on the opposite side being 

 absent. 



' In conclusion the author traces this dyke of serpentine pursu- 

 ing, its course in a direct line to the north-east and south-west of 

 the locality in which it occurs on the Carity. It is found recur- 

 ring at intervals for the space of at least 14 miles from the bridge 

 of Cortachie to Bamff, near Alyth, in Perthshire. 



It is always unconformable to the strata through which it 

 passes, and its course is never interrupted by any other rock. 

 . A notice was then read " On the Serpentine of Predazzo ;" 

 by J. F. W. Herschell, Esq. Sec. RS. 



In this communication, the author mentions that at Canzocoli, 

 near Predazzo, in the Tyrol, where a junction is seen of a gra- 

 nitiform sienite with dolomite, a layer of serpentine is found to 

 intervene between the sienite and the dolomite. 



The dolomite dips at an angle of 50° or 60° beneath the 

 sienite, and near the junction an alteration takes place in its 

 mineralogical character; as it presents, instead of its usual 

 highly crystallized saccharine structure, a flaky and very talcose 

 appearance. The incumbent sienite is no less affected. Its 

 grain is smaller, and it is intersected with innumerable veins 

 parallel to the plane of junction of a white mealy substance, 

 vyrhich partly dissolves with effervescence, and partly gelatinizes 

 with nitric acid. In the midst of this white substance occurs 

 the thin lamina of serpentine, which is extremely well charac- 

 terizied. 



The whole of the transition from the sienite to the dolomiti^. 

 takes place within a thickness of about 18 inches or two feet. , 



