Vol. 62.] BUTTERMERE AND ENNERDALE GRANOPHYRE. 267 



possession of orfchoclase, together with a rather basic plagioclase. 

 This association suggests a comparison with the monzonite-family of 

 Prof. Brogger, and the rock in question shows a distinct resem- 

 blance to his quartz-monzonites. Possibly it would be better to 

 regard it as related to the banatites, * which are subalkaline rocks 

 of the tonalite-group, containing typically a good deal of augite. 



A little farther to the north-east, between Mecklin Wood and the 

 farm known as Burnt House, is an interesting occurrence of a 

 rather fine-textured grey rock, which is much fresher than is usual 

 in this series. It occurs as an irregularly- shaped mass, about a third 

 of a mile long and 100 yards broad at the most. It appears to be 

 entirely surrounded by normal granophyre ; but it is very near the 

 margin of the latter, and is no doubt a forerunner like the last- 

 described. 



A slice of this rock [4772] is found to consist of plagioclase, 

 biotite, hornblende, augite, and quartz, with accessory magnetite and 

 apatite. The felspar is in the form of more or less ragged prisms 

 possessing the habit characteristic of the diorites or dolerites ; the 

 extinction is nearly straight, showing that it is oligoclase. A little 

 orthoclase is also present. Quartz is abundant, and its occurrence 

 is interstitial, but not granophyric. The biotite is very fresh, deep 

 brown in colour, and strongly pleochroic. Some of the most con- 

 spicuous elements in the rock are rather long narrow prisms of a 

 mineral which is usually very pale green or nearly colourless, with 

 a high index of refraction. Some crystals are non-pleochroic and 

 have a wide extinction-angle, up to 45° : others are pleochroic, and 

 have a narrow extinction- angle, usually below 10°, so that both 

 augite and hornblende are present. The hornblende is probably 

 secondary, of uralitic origin. These crystals are, no doubt, essen- 

 tially the same as the needles of augite which are so characteristic 

 of the margin of the gran ophy re-mass on the south-west of Seatallan 

 and elsewhere. 



The foregoing description shows that the affinities of this rock also 

 are with the tonalites and banatites, rather than with the granites, 

 since orthoclase is quite subordinate. It is essentially an augite- 

 bearing quartz-mica diorite, which is practically the 

 definition of a banatite. 



On the south-west side of Mecklin Wood is a rock of a much more 

 basic character. It forms a small mass, which is rather badly 

 exposed just above the stream, and close to the wall bounding the 

 wood. The mass is variable in character, but the bulk of it is a grey 

 rock of moderately-coarse texture, showing well-marked tabular 

 felspars, much dark mineral, and a little biotite and iron-pyrites. 



In slices [4773] it is seen to be doleritic in structure, although 

 many specimens are a good deal decomposed. It consists of zoned 

 columnar felspars, ranging from labradorite to oligoclase, enclosed 

 in typical ophitic fashion by large plates of a ferromagnesian mineral 



1 W. H. Weed & L. Y. Pirsson, 20th Ann. Eep. U. S. Geol. Surv. pfc. iii 

 1898-99 (1900) p. 471 ; also Am. Journ. Sci. ser. 3, vol. 1 (1895) p. 467. 



