Vol. 60.] ROCKS OF THE BORROWDALE VOLCANIC SERTFS. 99 



' Streaky ' rocks are met with at Measand Forces, at the top of 

 which banded ash is seen dipping eastward. Below the ' streaky ' 

 group a coarse rock occurs, which has the appearance of an Eycott 

 Lara. The line of junction between the two is vertical, and much 

 crushing has occurred at the junction. Between the two rocks on 

 Sand-Hill Knotts a iiue-grained. dark, basic rock occurs, and several 

 dykes of the same traverse the ' streaky' rocks, though not the rock 

 below. 



The ' streaky ' rocks run in a north-westerly direction to Colby, 

 frequently displaced by faults. They are developed on Great and 

 Little Birkhouse Hills ; a dark intrusive rock occurs below them. 

 Intrusive junctions may be seen, in which the 'streaky' rock becomes 

 reddish in colour and of a flinty character. The intrusive rock 

 is a quartz-diabase (3805). It seems very probable that the 

 Measand rock is also intrusive, and the two, with the diabase of 

 Walla Crag (on the other side of the lake), form a large intrusive 

 mass. 



Below the 'streaky' rock of Little Birkhouse Hill occurs a narrow 

 band of vesicular lava, separating it from the nodular rock 

 on Pinnacle Howe. This rock consists of oval nodules of flinty 

 material, the centre of which is either hollow or filled with quartz. 

 These nodules vary from half an inch, to 6 inches in length. The 

 same rock is again seen at the Old Quarry north of Fordingdale 

 Bottom, and thence it probably extends along the hillside to 

 Fordingdale Force, where an excellent section is exposed. It is 

 continued along the top of the slope to Laythwaite Crags, and on 

 round Whelter Combe in a vertical cliff about 100 feet high. The 

 succession here is — 



Feet. 



Compact garnetif erous rock 20 



Xodular rock 10 to 15 



Garnet ifero us rock with vesicles 50 to 60 



The nodular rock varies in thickness, and has a verv irregular 

 top and base. On Whelter Crags it splits into two, and is then lost 

 by faulting. Occurring again in the upper part of Randale Beck, 

 it runs to Kidsty Pike, where it is well developed in two bands. 

 This rock is not represented on the east side of Haweswater. On 

 p. 17, etc. of the Survey Memoir (quoted on p. 08) the rock is 

 described as 'bomboidal,' and considered to be of fragmental origin. 

 This is quite likely, for similar flinty fragments (with quartz de- 

 veloped in the centre of them) may be found in a compact ash 

 on Eagle Crag and Bosthwaite Fell, in the Borrowdale district. 

 Together with the quartz in the hollows, a black substance also 

 occurs, either forming a coat on the quartz-crystals or in oval graius. 



Above the great cliff of garnet-rocks in Whelter Combe, lavas 

 possibly of the Eycott type, vesicular lavas, and ashes are developed ; 

 and these are succeeded by a yellow, much-decomposed ' streaky ' 

 rock at the top of Bason Crags. 



Below the nodular rock-group, banded ash is seen, dipping 

 north-westward at an angle of 5°. Another band of garnet-rock is 

 found crossing the stream just above High- Whelter Farm — being 



a '2 



