ASSOCIATED METAMORPHIC ROCKS OF THE LAKE-DISTRICT. 595 



on the growth of the latter. In the examples shown in figs. 2 and 

 3, from a point in Lingmell Beck close to the granite junction 

 (Wastdale Head), the base is hazy and felsitic in ordinary light 

 (fig. 2), though having brown and greenish mica-flakes scattered 

 over it and in groups, with some grains of magnetite and pyrites. 

 But in polarized light, the ground shown in fig. 2 * appears under 

 crossed prisms as in fig. 3. As the axes of the prisms are slowly 

 brought at right angles to each other, the numerous small felspar 

 crystals seen in the figure gradually become distinct, whereas, before, 

 the hazy white base gave no indication of their existence ; sometimes, 

 however, with a |-inch objective and a strong light, very faint out- 

 lines of some of the crystals may be recognized. This may indeed 

 be called a crypto -crystalline structure. 



In other cases the felspar is distinctly and more largely developed, 

 both as orthoclase and plagioclase, and appears on the surface of the 

 rock generally in the form rather of felspar spots than of distinct fel- 

 spar crystals. Pig. 4 is an example taken from near the Eskdale 

 granite, west of Great How, which shows the crystalline structure 

 apparently carried a step further than in figs. 2 and 3. It should be 

 noticed that figs. 1 to 6, are all magnified to the same degree for the 

 sake of direct comparison. 



4. Fourth Stage. Bastard granite. — At the base of the northern 

 slopes of Scawfell Pikes, rather less than three quarters of a mile 

 from the nearest granite of Wastdale Head, occur several patches of 

 rock, to be described in detail elsewhere, which, viewed on the 

 outside, seem closely allied to the surrounding altered ashes, but 

 when examined with the aid of the microscope seem rather to belong 

 to the granites. An example of such is shown in PI. XXXI. fig. 5, 

 under polarized light. In these cases the base shows a transition 

 between the semicrystalline felsitic structure of the last stage, as 

 seen in figs. 2, 3 and 4, and the more defined and coarsely crystalline 

 structure of the true granite, as seen in fig. 6 (same scale). The 

 example drawn (fig. 5) is from a mass at the foot of Peers Gills, 

 beneath Plass Knotts, which can only be mapped separately from the 

 surrounding less altered ash rocks by means of a dotted, uncertain 

 line, on account of its somewhat more crystalline appearance, though 

 in some parts of this mass the original ashy bedding is still seen on 

 the weathered exterior with considerable distinctness. 



Yiewed microscopically, a good deal of free quartz is found to be 

 present; but this is not generally visible in hand-specimens with the 

 unassisted eye. The felspar crystals are of various sizes and both 

 orthoclase and plagioclase ; some are altered completely except 

 around the edges. The mica is both light-brown and pale-green, 

 the latter in greatest abundance and showing colours under crossed 

 prisms (see brightly banded portions in fig. 5). Both epidote and 

 pyrites also seem to occur in these rocks, and perhaps some magnetite. 



5. Fifth Stage. Granite. — Prom this last stage of metamorphism 

 (for I do not think any one can resist the united evidence of field- 

 work and microscopic examination to such gradual metamorphism) 



* Lower and left portion of disk. 



