GRANITE VEINS IN CORNWALL. 



249 



branches which cross the laminae of slate, cutting off both the quark 

 zose and argillaceous layers. The granite becomes much finer- 

 grained along the veins, and 

 nearly in proportion to their -SSili^E 

 smallness ; so that in the narrow- 

 est veins it is nearly compact. 

 Strings of fine-grained granite 

 divide the coarser sort 



Glen Tilt. In Glen Tilt, 

 MacCulloch has described nume- 

 rous and valuable facts of this ; 

 nature. At the bridge beyond 

 Forest Lodge, granite, hornblende 

 slate, and crystalline limestone 

 are very curiously associated. 

 Veins of red granite here divide 

 the other rocks, and enclose frag- 

 ments of them. The singular 

 interlacements of the rocks are 

 here shown by the sketch taken 

 1826. 



Fig. 57- 



Professor John Phillips in 



1. Crystalline limestone laminated by hornblende and red felspar in curved lines 

 or detached masses, round which the laminse of limestone bend, crossed by 

 granite and red felspar veins. 



2. White quartz rock and red felspar crystallised. 



3. Felspathic rock, red, with layers of black hornblende. 



4. Limestone laminated with felspar. 



5. The same with less felspar. 



6. Hornblende and felspar in layers. 



7. Laminated limestone. 



(a.) Red felspar vein a little quartz. 



8. 9. Hornblende, with layers, masses, and veins of white quartz and red fe'spar, 



which substances often occur together, making binary granite of very large 

 grain. 



10. Limestone, with red granite veins. 



1 1. Limestone, red granite veins, and white calcareous spar veins, which divide the 



granite veins. 



12. Red granite, composed of red compact or crystallised felspar, white quart,/, 



and black or gray mica, and encloses hornblende masses which are divided 

 by veins of granite ramifying from the general masses of thafc rock. 



Cornwall The extremity of Cornwall has long been famous 

 for the great variety of curious phenomena connected with the granite 

 veins which there divide the argillaceous slate, hornblende slate, 

 and greenstone rocks, all included by the miners under the title of 

 killas. So many writers of eminence, both English and foreign, have 

 described and reasoned upon these occurrences, that it is difficult to 

 select from the immense variety. The following is Majendie's account 

 of the veins at Mousehole, three miles south-west of Penzance : 

 " At this period the clay slate ceases, and the granite commences, 

 forming a promontory which runs out in a southern direction from 

 the central ridge. The slate is of a grey colour ; it is in strata nearly 



