from tin' Ni'K'Iumlx ])i"iitaiui .!//'/,">. < ! riijtialaiul IVest. 



As one or two grains with a general resemblance to the bastite appear 

 to give an oblique extinction, a third pyroxene may be present in 

 very small quantities. Mica is wanting as an original constituent, and 

 most of the iron oxide is secondary, but one grain may be primary. 

 The structure of the rock is granular, no constituent being idio- 

 morphic ; hence the order of consolidation cannot be determined with 

 certainty, but I incline to placing the olivine, which is slightly the 

 most abundant mineral, first, and the garnet, which is slightly the 

 least so, last. The rock is distinguished from ordinary Eulysite by the 

 presence of a fair amount of an enstatite, but as this does not indicate 

 any important difference in chemical composition, I prefer calling it 

 Enstatite-Eulysite, to burdening petrology with a new name. 



(/.) This specimen has a rude resemblance to an oven bottom loaf, 

 measuring full 16 inches in two directions at right angles on the 

 curved surface; the flat side being probably the result of a fracture, 

 apparently produced after most of the rounding had been done. The 

 rock is holocrystalline, its principal constituents being dull red garnets 

 and green pyroxenes. The former have their outer surface worn smooth 

 and flat, the latter a very slightly corroded one. The rock is rnacro- 

 scopically identical with the eclogite described in the last paper, and 

 it proves to be composed of pyrope and chrome diopside with 

 occasionally a few fibres of secondary hornblende, no grain either of 

 olivine or iron oxide occurring in the slice. 



(#.) This specimen is a rudely trapezoidal block with rounded 

 edges and corners, measuring about '2\ inches each way, apparently 

 rather water-worn, consisting of somewhat rounded crystals of greenish 

 pyroxene, over an inch in length, in a matrix of a similar mineral and 

 felspar. Specific gravity, 3*125. On examination with the microscope, 

 the larger grains prove to be generally diallage, a faint sea-green in 

 colour, with a close pinacoidal cleavage, often made more distinct by 

 the deposit of a little opacite or ferrite. Small brown negative crystals 

 are frequent, one of their longer edges lying parallel with an axis of 

 elasticity. This mineral is altered locally into a pleochroic hornblende 

 (changing from a raw to a burnt umber tint). The diallage is some- 

 times bordered by, and near its edges occasionally encloses, small grains 

 of a slightly browner and more pleochroic mineral, extinguishing 

 parallel with its principal cleavage, and thus representing a rhombic 

 pyroxene,* but it also throws out root-like prolongations in which a 

 cross cleavage is visible. Where the diallage has been replaced by 

 hornblende, the latter often extends some little distance into the mots, 

 which in a few cases suggest the presence of the rhombic constituent. 

 These are embedded in felspar, thus affording a pegmatitic structure 

 which varies in different parts of the slices from incipient to well 



* These locally are seen to pass into a yellowish serpentanoiu mineral, \vlii.-li 

 vvith crossing nicols shows a fibrous structure and fairly bright polarisation (ints. 



