592 



J. CLIFTON WARD ON THE GRANITIC, GRANITOID, AND 



the frequent porcelainic appearance of these beds are often sufficient 

 to indicate the original nature of the deposit. 



3. Second Stage. — The next stage is that the altered rocks begin to 

 assume a marked purple tint, and minute specks of mica appear, 

 which increase in abundance and are sometimes collected into nests 

 as the granite is more nearly approached. 



4. Third Stage. — Finally, there are developed in this purplish 

 micaceous base many small crystals of felspar, which often have 

 an irregular and hazy outline ; and occasionally quartz also be- 

 comes visible. Such extremes of metamorphism represent, indeed, 

 examples of fine-grained granite, which in outward appearance are 

 intermediate between the true granitic mass and the less highly 

 altered rocks, often retaining something of their old ashy character 

 on the weathered exterior. 



5. Boundary -lines of granite. — Nevertheless it is generally the 

 case that the transition from the metamorphosed ashes, or the 

 very fine-grained granite, to the true granite, appears somewhat 

 sudden, the rock for the most part only losing its dark and purplish- 

 blue hue and becoming lighter in colour immediately at the junction. 

 In the case, however, of metamorphosed coarse ashes or breccias, 



Pig. 2. — Sketch Map of part of the Lake-district, to show the posi- 

 tions of rocks figured on PI. XXXI., and of those analyzed {see 

 p. 597). Scale T 7 ^ inch to 1 mile. 



4 XirTc Fell 



it* 



i£ca£ellPikts 



\tf- / Great Wow 

 J? MA Anal¥ l l £i?gU S ida 



A F fr 6l < 



Analysis', 



. ri ,, Analysis. 1. 

 tprcen Gable a, 



Aflase Brown, 

 i Great Gable 



No geological details are placed upon this map, as they will be found fully 

 shown upon the published Survey maps. 



a. Position of highly altered ash figured in the Survey Memoir on " the Geology 



of the northern part of the Lake-District," plate ii. figs. 15 and 16. 



b. Position of highly altered bedded! ash figured in the paper entitled "Notes on 



the Microscopic Bock-Structure of some Modern and Ancient Volcanic 

 Rocks," Quart. Journ. Geol. Soc. vol. xxxi. plate xvii. fig. 10. 



