518 THE CONTINENTAL ORIGIN OF FI.TI, II., 



In addition to the isolated crystals of augite scattered through 

 the base, there are a few rosettes of crystals up to about a couple 

 of millimetres in diameter. 



The only other mineral to be noted is magnetite in grains and 

 crystals up to about h mm. in diameter. 



Some peculiar granular aggregates occur. They consist of 

 small grains of rather more greenish augite than that noted 

 above, clear basic felspar, magnetite, and a little brov/n glass 

 similar to that composing the base. The}* range up to about 

 I mm. in diameter. 



As stated above, one of the most remarkable features of the 

 rock is the exceptional development of inclusions in the felspar. 

 In all instances they appear to be mainly tabular; and some 

 sections, particularl}' those in the zone perpendicular to (010) 

 giving extinction angles near the maximum, are apparently quite 

 free from them. This is probably due to the fact that the inter- 

 positions have their maximum extension in (010), while their 

 thickness is very small; or else such sections, being more or less 

 through the centre of the crystal, have missed the crowded parts 

 which are on the whole more towards the exterior. The indi- 

 vidualised inclusions are of three kinds : — 



(1). Faint greenish grains whose refractive index and double 

 refraction indicate augite. The uniformity of distribution of 

 their polarisation colours confirms the statement that they are 

 platy. 



(2). Clear prisms of minute size, perhaps slightly greenish in 

 colour. Their refractive index is considerably higher than that 

 of the felspar. They are crossed by a marked parting perpendi- 

 cular to their length, and possess a noticeable double refraction. 

 The extinction angle measured from the long axis of the prism 

 is large, angles up to 45^ being met with. The orientation is on 

 the whole irregular, but sometimes short rods are arranged end 

 to end in straight lines, with very small spaces between them, 

 like the carriages of a railway train. They are especially abun- 



