354 



DESCRIPTION OF THE ROCKS. 



As already stated these rocks usually occur as small dykes or veins. 

 They frequently show a tendency to spheroidal weathering. Sometimes 

 the constituents of the rock, especially the felspar, show a tendency to 

 radial grouping so that spheroidal structures (1 c.m. in diameter) may 

 arise (kugelminette). This is often a contact phenomena. The mode 

 of alteration, the abundance of brown mica in the typical rocks and 

 the frequent presence of carbonates, when taken in connection with the 

 mode of occurrence, are the most characteristic features of the group. 

 It will be seen from the above descriptions that, like all other petro- 

 graphical groups, it is very ill-defined. A rigid definition can only be 

 given to the group by ignoring transitional forms, which after all 

 are as abundant as the typical forms. 



Kendal and Sedbergh Districts. These rocks have been described 

 by Messrs. BONNEY and HOUGHTON. They vary considerably in colour 

 from pale grey to dark grey with reddish, brownish and purplish tints. 

 Mica is abundant in most of them. The state of preservation often 

 makes it difficult to speak positively as to the original character of 

 the felspars and of the ground-mass. Microlites of felspar and augite 

 occur in some of the ground-masses. Augite also occurs in definite 

 crystals. In the rock of the highest dyke in Helm Gill Professor BONNEY 

 observed a fan-like grouping of the felspars. Biotite occurs not only 

 in macroscopically-recognizable crystals but also as a constituent of 

 the ground-mass in some of the porphyritic rocks. The authors classify 

 the dykes as follows : 



MINETTE : Cross Haw Beck. KERSANTITE : Bed of Lune and Holbeck 

 Gill. MICACEOUS DIORITE: Gill Bank and Stile-End Farm. MINETTE- 

 FELSITE : Near Windermere Station ; Kendal Road ; Railway, Docker 

 Garth ; South of Haygarth ; Helm Gill ; Backside Beck. KERSANTITE- 

 PORPHYRITE : Uldale Head ; Wattle Gill ; Westerdale. PORPHYRITE : 

 Barley Bridge. 



The minette contains augite and is therefore an augite-minette. 

 The micaceous diorites answer to Professor ROSENBUSCH'S camptonites. 

 The following analyses of these rocks are by Mr. HOUGHTON : 



Al,0 3 



FeA 



FeO 



MnO 



CaO 



MgO 



K 2 



Na 2 



H 2 



C0 2 



100-59 100-96 99-07 100-58 97-05 100-72 98-90 99-81 



