78 de. a. e. dweeeyhoese on inteusiv'e bocks [Feb. 1909, 



considerable quantity. Further, iD the minor intrusions biotite 

 is present in large quantity, while in the granite muscovite is the 

 dominant mica. There are also pseudomorphs after either a 

 pyroxene or an amphibole, both of which minerals are absent 

 from the normal granite of both Eskdale and Wasdale Head. 



(d) The Eskdale and "Wasdale Granites and their associated 

 dyke are much more acid than any of the other rocks hitherto 

 mentioned, and they show comparatively little alteration, with the 

 exception of that due to weathering along the great lines of 

 dislocation occupied by the iron stone-veins. They are undoubtedly 

 intrusive in the Borrowdale Series, and the western boundary of 

 the main intrusion, as shown on the maps of the Geological Survey 

 and as confirmed in the field, very strongly suggests that they are 

 pre-Triassic. Unfortunately, no clear exposure of the junction with 

 the Trias could be found ; but the similarity of the relation which 

 the Triassic outcrop bears to the granite and to the Borrowdale 

 rocks is strong evidence of the existence of the granite before the 

 Triassic Period. It seems probable that this intrusion belongs 

 to the Devonian Period, as does the neighbouring granite of Shap, 

 which, with the exception of its large phenocrysts of orthoclase, is 

 not dissimilar to some of the varieties of the Eskdale Granite (as, 

 for example, the Wabberthwaite variety). 



(e) The basic intrusions have not yet been examined, except in 

 one or two instances where they come into proximity to the 

 granite. They are, however, undoubtedly the latest intrusions 

 in the area, and may be seen cutting and displacing any of the 

 others with which they come into contact. Although basic in 

 composition and containing olivine, they are much less altered 

 than any of the other intrusive rocks. They may well be connected 

 with the great Tertiary basic flows of Antrim, as has, I believe, 

 been suggested by Mr. Harker. 



My thanks are due to Mr. P. H. Pastall for information 

 respecting the neighbouring intrusion of granophyre ; to Mr. Cosmo 

 Johns for many facts recently added to our knowledge of the 

 structure of alloys ; and to Messrs. C. G. Jackson & G. V. Wilson 

 for analyses of rock-specimens. 



EXPLANATION OF PLATE III. 

 Pig- 1. Crystal of perthite (orthoclase-oligoclase) in Eskdale Granite. Slide 78, 

 magnified 23 diameters. See pp. 61-62. 



2. Quartz embedded in oligoclase, Eskdale Granite. Slide 66, magnified 



23 diameters. See p. 63. 



3. Phenocryst of quartz in the marginal variety of the Eskdale Granite. 



Slide 7, magnified 12 diameters. See p. 63. 



4. Quartz-mosaic from the margin of the Eskdale Granite. Slide 80, 



magnified 23 diameters. See pp. 63 & 65. 



5. Junction-breccia from near Stony Tarn. Slide 131, magnified 16 dia- 



meters. See pp. 67-68. 



6. Junction of granite (a) and altered Borrowdale lava (b), near Stony 



Tarn. Slide 81, magnified 23 diameters, See p. 66. 



