594 J. CLIFTON WAED ON THE GRANITIC, GRANITOID, AND 



is mainly due to an immense number of very minute particles of 

 chlorite, which frequently take the form of flowing lines around 

 imbedded fragments or crystals, thus giving rise to the streaky 

 appearance. 



2. Second Stage. Felstone-Wce with a purplish hue. — Yery good 

 examples of this stage of alteration may be met with in Great Gable 

 and many other parts around "Wastdale. 



The base, though somewhat felsitic, shows under crossed prisms 

 a dark ground with scattered points of light. This dark ground 

 seems mainly due to the presence of innumerable minute particles of 

 brown mica, apparently taking the place of the chloritic particles 

 observed in the previous stage. There generally occur in this base 

 a few indistinct, altered fragments of felspar, occasionally a long 

 tube-like crystal, more or less epidote, and a few specks of pyrites. 



In some cases, as in the example from Bell Rib, Yewbarrow (PI. 

 XXXI. fig. 1), the brown mica particles are collected in clusters, in 

 the midst of some of which are black patches, probably caused by 

 decomposition of the same. In such instances as these, the rock, 

 though often fine-grained, occasionally shows its ashy structure (as in 

 the figure) or distinct lines of bedding on the outside, while it breaks 

 with a conchoidal fracture and is often exceedingly trap-like within. 



Then there are other cases in which, while the general base 

 appears felsitic, the scattered particles seem to be partly chlorite 

 and partly brown mica; and there occur, in many spots, small 

 needles of felspar, which however, only appear under crossed prisms, 

 and have sometimes a disposition to set round the larger crystals, 

 and fragments. Besides this setting of the crystalline needles, there 

 seems to be in some cases a general tendency to a flow of the granules 

 (chloritic and micaceous) among which they are imbedded ; but this 

 only appears where there are comparatively large fragments in the 

 field around which it may take place. It is a curious fact that, in 

 the rather exceptional cases in which the small crystalline needles 

 occur, they are not visible except under crossed prisms; in ordinary 

 light the very same part of the base appears felsitic (hazy ground 

 with scattered particles), which, when polarized light is used, and 

 the prisms are crossed, shows the fine needles. Of course it is quite 

 possible that in such cases we have, mingled with the highly altered 

 fragmental rocks, some of the true lavas ; but the great thickness of 

 some of these rock-masses (as between Cold Pike and Wrynose) and 

 the insensible gradations into unmistakable ash rather tend to 

 negative this view ; and if so, we are led to regard the se/racrystalline 

 structure as produced under special circumstances by intense alter- 

 ation. 



3. Third Stage. Purplish base with imperfect crystals porphyri- 

 tically imbedded. — In this third marked stage the mica particles are 

 more clearly developed and occur in great numbers, frequently col- 

 lected into groups, as seen in PI. XXXI. figs. 2, and 3 *; they are also 

 more distinctly flaky, and are sometimes collected thickly around the 

 edges of imperfectly formed felspar crystals, as if pushed outwards 



* See the upper and right-hand portion of the disk. 



