ASSOCIATED METAMORPHIC ROCKS OF THE LAKE-DISTRICT. 3 



This rock, misnamed Hornblende Slate, is frequently well jointed, 

 and has furnished a great many boulders which have been transported 

 southwards out of the tract of Skiddaw Forest. Its texture has also 

 favoured its use for making sets of musical stones, several of which 

 may be seen in Keswick. 



4. Third Stag.' of Alt-ration : Mica-schist. — The spotted schist, 

 becoming increasiugly micaceous, passes over into mica-schist, 

 which, however, is seldom well and typically developed, except close 

 round the margin of the granite. It generally retains more or less 

 of the spotty character, the spots becoming more and more faint, 

 while sometimes crystals of chiastolite also occur. 



The general colour of this schist is alight grey, passing into bluish 

 grey. The foliations are wonderfully contorted, as may be especially 

 well seen near the granite, at the junction of Grainsgill Beck with 

 the river Caldew. This rock also weathers in places into large blocks, 

 which often lie thickly strewn upon the mountain-slopes ; but in other 

 parts it readily crumbles away, forming a sandy wash. 



5. Granite and its Junctions with the Altered Roelcs. — The granite, 

 around which these altered rocks lie, occurs in three detached masses, 

 a small patch exposed in Sinen Gill (101 S.E.), a larger in the upper 

 course of the Caldew, and a third a little lower down the same river, 

 and extending northwards to the foot of Brandy Gill (101 X.E.). 

 There is a fourth small area of granite at the head of Brandy Gill ; 

 but it is only poorly developed, and is much decomposed by weather- 

 ing. It is surrounded by other rocks than Skiddaw slates, and will 

 therefore be dealt with elsewhere. 



The Sinen- Gill and upper Caldew granites are precisely similar in 

 character, consisting of white felspar and dark mica ; and the Brandy- 

 Gill rock differs but slightly, and that principally on the north, where 

 it borders on rocks which do not belong to the Skiddaw Series. 



In almost every case observed the junction between the schist and 

 the granite is well marked. Occasionally the schist at the point of 

 junction is the dark and spotted rock, in which case the line of di- 

 vision between the two is very clear ; and in no instance is there any 

 difficulty in drawing a geological boundary to these three granitic 

 masses. Sometimes close to the granite the rock becomes a little 

 gneissic ; but there is no general passage from mica-schist into gneiss 

 and from gneiss into granite. 



II. Microscopical Examination. 



The microscopic structure of the chiastolite slate and spotted schists 

 has been figured in the Official Survey Memoir on 101 S.E. ; but the 

 accompanying illustrations in Plate I. will, I think, throw additional 

 light on the minute structure of these rocks. As in the preceding 

 section of the memoir, one figure shows the actual junction of the 

 granite and met^amorphic rock. 



1. Chiastolite Slate. (Plate I. fig. 1.) — The example figured is a 

 fairly typical specimen of chiastolite slate. In many parts the non- 

 crvstalline characler of the base is clearly seen, the various particles 



b 2 



