Junction of the Granite and the Killas Rocks in Conmall. 165 



of a porphyritic appearance, with large crystals of felspar; but 

 in the distance of one foot from the junction with the killas, 

 occurs fine-grained granite without these large crystals. The 

 junction between both rocks is very distinct, but they hang to- 

 •rether ; and it is easy to get specimens which' present both 

 rocks in one piece. The junction of both rocks is nearly pa- 

 rallel to the strata of the killas, of which the lower part ap- 

 pears more stratified than the upper part, which is very com- 

 pact. From the granite comes forth a vein {b) into the killas, 

 two inches wide, consisting of a fine-grained granite like the 

 variety of the main body of granite that occurs near the junc- 

 tion with the killas: no interruption is here to be seen; only 

 an open chasm begins here, and intersects the granite as far as 

 the bottom of the cove. The upper end of this granite vein 

 is not to be seen. The granite vein (c) is a little wider than 

 that just mentioned; it is to be seen on the whole height of 

 the wall. An adit is wrought in it, perhaps in search of tin 

 ore. The vein {d) ends at a height of sixteen to twenty feet 

 above the main body of the granite ; in the same way as does 

 the vein {e). A small string runs from this vein to another (/), 

 of which the upper termination is not easily to be seen. The 

 vein {g) is four to five inches wide, forming in one place the 

 shape of a hook, and will probably be seen in the upper part 

 of the wall, which is not in the same plane as the lower part. 

 The whole height of this vein is very nearly 250 feet above the 

 bottom of the cove. The vein {h) divides into two branches. 

 The vein ( i ) has been worked away to a considerable height, 

 as we suppose for tin ore : we were prevented by the sea from 

 reaching this vein and that more to the south. 



These granite veins intersect some of the quartz veins that 

 occur frequently in the killas, and are intersected by others. 

 The component of these veins is a fine-grained granite, quite 

 the same modification that is also found in the main body of 

 the granite. 



III. Cape Coymwall.—Yeim of granite frequently occur in 

 the killas near to the junction of this rock and the granite in 

 Port Just Cove at Cape Cornwall ; one of them is represented, 

 fig. 4. It is six inches wide, runs nearly 30 degrees south 

 of west, and dips to the south, the angle with the horizon 

 being 49 degrees. It may be traced to a length of twenty- 

 four leet, and a height of%ix feet. The strata of the killas 

 run 7 degrees south of west, and dip with an angle of 

 26 degrees to the north ; they are heaved by a granite vein, 

 as will ajipcar from a vein of quartz in the killas, and not in 

 the regular way, but so that the solid forming the north wall 

 of the vein is at a lower level than the south wall of it. The 



texture 



