22 



J. CLIFTON WARD ON THE GRANITIC, GRANITOID, AND 



altered augite ; but both are a great deal changed. The divisions 

 which appear so frequently to traverse the small clear spaces appear 

 only in polarized light. This kind of crypto-crystalline structure is 

 akin to that described in Part II. of this Memoir as occurring in a 

 highly altered volcanic rock close to the granite. 



These fine-grained bedded portions are quite distinct from irre- 

 gular segregations, some of which occur in the coarse-grained 

 hypersthenite lower down the same hill-side. These last are of 

 irregular form, often more or less circular, of a whitish tint, and 

 fine-grained. Microscopic examination shows them to consist of a 

 compound of well-developed felspar crystals, a green hornblendic- 

 looking mineral, and quartz. 



III. Chemical Examination. 



1. Bodes of St. John's Vale and of Buttermere. — The following 

 are analyses of carefully selected specimens of (A) altered SkiddaAV 

 Slate from the summit of Red Pike, (B) St.-John's quartz felsite, 

 (C) Buttermere syenitic granite. (See figs. 3, 2, and 5, Plate II.) 





A. 



B. 



c. 



D. 



E. 





Skid. Slate 



Quartz 



Syenitic 



Mean of 

 two Skid. 



Slate 

 analyses. 



Coarse 





of Eed 



felsite of 



granite of 



ash 





Pike. 



St. John's. 



Buttermere. 



(altered). 



Silica 



54-480 



67-180 



71-442 



60-102 



68-421 



Alumina 



20-720 



16-650 



15-340 



17-451 



15-855 



Lime 



1-624 



2-352 



1-064 



1-400 



2-016 



Magnesia 



1-946 



1-549 



•720 



2-144 



•792 



Potash 



3-203 



2-914 



4-439 



3-232 



3-338 



Soda 



6-217 



4-032 



3-951 



4-099 



5-627 



Ferrous oxide . . 



8-188 



2-151 



1-107 



7-747 



2-855 



Ferric oxide . . 



•988 



•559 



1-230 



•494 



•172 



Phosphoric acid. 



•569 



•179 



•118 



•284 



•204 



Sulphuric acid . . 



trace 



trace 



trace 



•147 





Carbonic acid . . 



trace 



•885 



trace 



trace 



trace 



Loss on ignition 



2-065 



1-549 



•589 



2-899 



•720 





100-000 



100-000 



100-000 



99-999 



100-000 



In the fourth column is the mean of two extreme analyses of 

 Skiddaw Slate, that of A and that of the How-Gill slate brought 

 forward in Part III. The result is a very near approximation to 

 Haughton's analysis of Welsh roofing-slate (see page 5, Part III). 

 In the fifth column I have reinserted an analysis of coarse altered 

 ash, brought forward in Part II. of this memoir *. 



The question now arises, Have we any evidence, in chemical com- 

 position, to enable us to decide whether the quartz felsite of St. 

 John's or the syenitic granite of Buttermere has been formed deep 

 * Quart. Journ. Gteol. Soc. vol. xxxi. p. 597. 



