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



Of these analyses, No. 1 is of unmetamorphosed slate, Nos. 2-5 

 contain the small concretions and mica, gradually increasing in the 

 number and size of its flakes, and No. 6 shows the composition of 

 Cornubianite, an extremely hard and crystalline metamorphic rock. 

 The author observes that these analyses prove the metamorphism not 

 to consist in an increase or loss of chemical elements, but rather in a 

 chemical or mechanical change among those previously existing in the 

 rock, and regards the cause of this change, whether the direct action 

 of the granite or watery influence alone, as still an open question. 



Kenngott alludes to Knotenschiefer, in his 'Elements of Petrography,' 

 as a rock of an uncertain character to which various names have been 

 given, such as Fleck-, Frucht-, or Garbenschiefer, according to the 

 appearance of the small spots, and which should be definitely named 

 when recognized minerals such as chiastolite &c. are present. 



The metamorphosed Skiddaw slates have been thus described by 

 various observers : — 



In 1820 Jonathan Otley, whose name will always be held in re- 

 verence in the Lake-district, first separated the Skiddaw slates as a 

 group from the other neighbouring formations*, and noticed the 

 "mica slate," the " whintin" (=spotted schist), and the " chiastolite 

 slate " developed around the granite. (See Otley's ' Guide to the 

 Lakes.') 



In 1824 and following years Prof. Sedgwick carried on his un- 

 tiring and thorough investigation of the district. In 1832 he thus 

 writes of the Skiddaw group where metamorphosed f : — " (1) Skiddaw 

 slate with interspersed crystals of chiastolite, alternating with and 

 passing into the preceding group (unaltered Skiddaw slates). (2) A 

 similar slate with numerous crystals of chiastolite, passing in the 

 descending order into a crystalline slate sometimes almost composed 

 of matted crystals of chiastolite. (3) Mica-slate spotted with chias- 

 tolite. (4) Quartzose and micaceous slates sometimes passing into 

 the character of gneiss." 



The same author, in his ' Letters,' dated 1842, says " I believe 

 that this beautiful mineral group is nothing more than the Skiddaw 

 slate altered and mineralized by the long-continued action of subter- 

 ranean heat. The granite, though a fused rock, may not have pro- 

 duced the whole of this change ; but it is at least an indication of the 

 kind of power by which the " metaniorphic structure was brought 

 about." 



Otley, in the article already quoted, first drew attention to the 

 distinction between cleavage and stratification in connexion with 

 these rocks ; and Sedgwick, in 1835, gave a definition of cleavage. 



Prof. Harkness, in 1858, alludes thus to the rocks in question : — 

 " This Skiddaw slate (on the north side of the granite), as it approx- 

 imates the granite of Skiddaw Forest, passes into chiastolite slate, 

 chiastolite rock, and a pseudo- gneiss. On the south side of the gra- 



* " Remarks on the Succession of Rocks in the District of the Lakes," Phil. 

 Mag. vol. lvi. p. 257 (from the Lonsdale Magazine, vol. i. p. 433). 



t " On the Geological Relations of the Stratified and Unstratified groups of 

 rocks composing the Cumbrian Mountains," Proc. Geol. Soc. vol. i. p. 399. 



