102 MR. E. E. WALKER ON THE GARNET-BEARING [Feb. I904, 



sufficient amounts of the mineral from the intrusive rocks for 

 analysis it would be necessary, in the majority of cases, to have 

 recourse to separation by heavy liquids. The garnets analysed 

 were obtained from the garnet-ash of High-Goat Gill, the 'streaky' 

 ash of the prominent crag west of Galleny Force, and the ashes 

 of Illgill Head and Sty-Head Tarn. Titanium is present in all 

 four, and only a small percentage of the iron is in the ferric state. 

 It is not unlikely that water may occur in these garnets, but no 

 estimations were made. 



The most frequent change that the garnets undergo is a con- 

 version to greenish chlorite with separation of iron-ore. Generally, 

 the change proceeds irregularly from the outside to the centre. 

 In a ' streaky ' rock from Lady's Seat (Mardale), the garnets give 

 rise to flakes of chlorite in a direction at right angles to that of the 

 cleavage in the rock. Under great pressure the garnets lose their 

 reddish colour, become a dirty brown, and pass gradually into an 

 aggregate of chlorite and a sericitic mineral. 



I wish here to express my thanks to Mr. Charles Smith, formerly 

 at the Mineralogical Museum, Cambridge, for all the help which he 

 gave in the preparation of rock-sections containing special garnets. 



X. Metamorphism oe the Volcanic Koces. 



The metamorphism of volcanic rocks by a granitic intrusion has 

 been thoroughly dealt with by Messrs. Harker & Marr ! in their 

 papers on the Shap Granite and associated metamorphic rocks, and 

 by Mr. Harker- in his paper on the Carrock-Fell Gabbro. 



The metamorphosed rocks round the Eskdale Granite show very 

 much the same characters. The rocks in which new minerals are 

 developed are either ashes or Eycott Lavas. These become choco- 

 late-brown in colour, owing to the development of aggregates of flakes 

 of an inteusely-pleochroic brown mica, probably produced from 

 chlorite. Close to the intrusive junction a very pale-green mineral 

 is developed, forming either irregular masses or elongated prisms 

 giving high polarization-tints. This mineral, as before mentioned, 

 becomes absorbed into the intrusive rock. The mineral may be a 

 fibrous hornblende. 



The extreme type of metamorphism is furnished by xenoliths of 

 purple ash, enclosed in the intrusive quartz-porphyry. Examples 

 occur west of Stony Tarn (3887) and at Piers Gill. ^Numerous 

 brown mica-flakes occur in a holocrystalline mass of quartz and 

 plagioclase. The two last-named minerals are hard to distinguish 

 one from the other, both being perfectly clear. 



Garnets with very irregular outline are also produced, the border 

 being of a very spongy character freely penetrated by quartz and 

 plagioclase. The process of formation of these garnets appears to 

 be most interesting. At first, there is a confused mass consisting 



1 Quart. Journ. Geol. Soc. vol. xlvii (1891) pp. 292-309 & vol. xlix (1893) 

 pp. 360-65. 



2 Ibid. vol. 1 (1894) pp. 331-34. 



