Vol. 62.] BTJTTERMEEE AND ENNEEDALE GBANOPHYEE. 269 



The mineralogical composition is singularly uniform, and the 

 more basic modifications consist essentially of the same minerals in 

 different proportions, if we regard the biotite and augite as closely 

 related, an assumption which seems justified by the evidence. 



So far as structure is concerned, it is especially characterized by 

 micrographic or micropegmatitic intergrowth, due to simultaneous 

 crystallization of the quartz and felspar. 



The earliest phase of intrusion is that of small masses of more 

 basic character, which now occupy a marginal position ; these may 

 be described as ranging from dolerites and quartz-dolerites to a 

 type in which the presence of a considerable proportion of orthoclase 

 shows affinities to the quartz-monzonites of Prof. Brogger s classifica- 

 tion. This was quickly followed by the intrusion of the main mass, 

 while the earlier injections were in some cases still hot and partly 

 liquid. 



A noteworthy feature is the absence of any well-developed series 

 of dykes of the more acid rocks. A few examples of dykes exist in 

 the more northern part of the area, but those in the southern part 

 seem to belong entirely to the Eskdale Granite. 



• In view of the abundance of garnet-bearing rocks in the central 

 part of Lakeland, it is worthy of notice that I have not observed a 

 single occurrence of garnet in any one of the very numerous specimens 

 examined. The late E. E. Walker noted the occurrence of loose 

 blocks of garnet-bearing rocks in Burtness-Cornbe Gill, and, chiefly 

 on this evidence, stated his belief that the Buttermere-Ennerdale and 

 Eskdale intrusions were derived from the same magma. 1 He did not 

 see these rocks in situ, and I have observed nothing either there or 

 elsewhere to confirm this idea : in fact, what evidence there is points 

 the other way, although it must be admitted that it is chiefly negative 

 evidence. 



With regard to the age of the intrusion, I do not feel competent 

 to express an opinion. The only evidence bearing on the point so 

 far obtained, is the absence of cleavage on the north side of the 

 Buttermere laccolite, which seems to show that the Skiddaw Slates 

 on this side were protected from the influence of the great thrusts 

 coming from the south-east, which so strongly cleaved them in other 

 parts of the district. The intrusion was, therefore, previous to the 

 great earth-movements of the later part of the Caledonian series. 

 Whether it accompanied the Ordovician movements of the same series 

 remains to be proved. 



On reference to the map (fig. 1, p. 254), it will be seen that the 

 Ennerdale and Eskdale intrusions come together at the foot of 

 Wastwater. It might be expected, therefore, that this locality would 

 possibly throw some light on the question of their relative ages. I 

 have not been able to find any section showing both rocks in contact, 

 since the probable line of junction is much-covered by scree-material. 

 Dr. A. II. Dweriwhouse, F.G.S., kindly informs me that he has 

 been equally unsuccessful; a casual inspection seemed to show 



1 Quart. Journ. Geol. Soc. vol. lx (1904) pp. 84-85. 

 Q.J.G.S. No. 246. T7 



