8 J. CLIFTON WARD ON THE GRANITIC, GRANITOID, AND 



planes of foliation ; and mica appears, often in considerable quantity, 

 probably formed from some of the andalusite or rectangular spots. 



6. The spotted schist passes into mica-schist, consisting of quartz 

 and brown and white mica, but frequently retains, to the last, faint 

 spots, and occasionally chiastolite crystals. The planes of foliation 

 in the mica-schist are very much contorted all round the granite 

 margin. 



7. When viewed microscopically, the chiastolite slate is found to 

 contain in many parts small crystals, besides the large ones of 

 chiastolite, and the spots, which last are often plainly seen to be 

 but undeveloped chiastolite. 



8. In the spotted schist the chief difference, microscopically, is 

 the increase in number of the spots and of the minute crystals in 

 the base, while mica begins to appear pretty plentifully (taking 

 the place of some of the andalusite), and there is some quartz. 



9. Lastly, in the mica-schist the andalusite and the spots give 

 way more and more to mica and quartz. 



10. Chemically, the altered rocks differ chiefly from the granite 

 in containing far less silica and much more alumina and ferrous 

 oxide. The analyses of the spotted and mica-schists are very 

 nearly identical ; that of the chiastolite slate shows more silica and 

 less alumina, but is in other respects similar to the analyses of the 

 schists, though it contains more carbon. 



11. On the whole, the evidence seems to be against regarding 

 the granite, now exposed, as the result of the extreme metamor- 

 phism of the Skiddaw slates immediately around it; but whether it 

 may not have resulted from the metamorphism of underlying parts 

 of the same series is an open question. The great contortion of the 

 mica-schist may be in part due to the, at any rate partially ', intru- 

 sive character of the granite. 



Appendix. 



The following papers by foreign authors have been written on rocks 

 similar to those just described : — 



Naumann, "Knotenschiefer," Erlauter. z. geogn. Karte v. Sachsen, 1838, No. ii. 



p. 264, and 1845, No. v. p. 50. 

 Kersten, " Knotenschiefer, ' Journ. f. prakt. Chemie, vol. xxxi. p. 108. 

 Durociier, "Etudes sur le metamorphisme des roches," Bullet, de la Soc. geol. 



de France, 1846, vol. hi. p. 546. 

 Carius, " Thonschiefer-Metamorphose bei Eichgriin," Leonh. u. Br. Jahrb. 1856, 



p. 595. 

 Muller. " Knotenschiefer," Berg- u. huttenm. Zeitung, 1858, p. 107. 

 Jermeejeff, Prm., "Ueber russische Andalusite," Verhdl. d. k. Ges. fur die ges. 



Mineral. St. Petersburg, 1864, pp. 135-147. Leonh. Jahrb. 1866, p. 724. 

 Kenngott, Elemente der Petrographie (1868), p. 207. 

 Fuchs, " Die alten Sediment-Forniationen und ihre Metamorphose in denfran- 



zosischen Pyrenaen," Leonh. Jahrb. 1870, p. 717. 



For microscopic descriptions of the minerals andalusite and chias- 

 tolite, see also : — 



Zirkel, Mikroskopische Beschaffenheit. 

 Rosenbusch, Mikroskopische Physiographic 



