

102 



characters of the mica have been already described. The hornblende is 

 pale green by transmitted light, and shows a pleochroism which is characteristic 

 but not strongly marked. Sometimes it contains tabular inclusions, which 

 have suggested to Professor JI:DD that it may have been derived from diallage. 

 Serpentinous pseudomorphs occur in the hornblende, and their characters are 

 thus described by Professor JUDD : " Examined with high powers of tlu; 

 microscope, this serpentine is seen to be filled with black and brown 

 enclosures, some rod-like and stellate in form, others of a tabular character. 

 Sometimes these inclusions are arranged in one set of parallel planes only ; in 

 other cases they lie in two sets of planes intersecting one another. There can 

 be no doubt that much of this serpentine is pseudomorphous after olivine ; 

 but some of it may replace enstatite." The relative proportions of the 

 different materials have been estimated by making a number of drawings 

 with the camera lucida and then cutting out and weighing the portions which 

 represent the different minerals. The result obtained by Professor JUDD is 

 as follows : 



Hornblende . . . . 58 '5 per cent. 



Serpentine . . . . . . 22'0 



Altered mica . . . . . . 18'5 



Magnetite and accessory constituents 1/0 



The chemical composition of the rock is given in the following table 

 of analyses. 



ANALYSES OF BRITISH AND FOREIGN ROCKS BELONGING TO GROUP A. 



I. II. III. IV. V. 



100-15 101-:-5 ( .)9-4C 99-317 99-39 

 3-287 3-269 2'93 2'960 



