OF THE DEPENDENT ISLES OF TAIWAN. 43 



and crystalloids of violet-brown augite, magnetite, and xeno- 

 morpliic olivine, with the interstitial mass of analcime and 

 base. The laths are multiple-tsvinned with the parapet-like 

 terminations {PL II, Fig. ö) produced by the shifting of lamellse 

 to the one end or the other with reference to the adjacent plate. 

 The slide treated with HCl shows a considerable corrosion of 

 the interior lamellœ of the laths, while the exterior remains 

 intact and fresh, as if a frame is enclosing the hollow space. 

 The crystals of a violet-brown augite of the short prismatic habit, 

 rather flattened towards the ortho-axis, are freely developed, or 

 occur in clusters. The augite and plagioclase must have, there- 

 fore, crystallized simultaneously, and at their contact the one 

 is partially penetrating the other and vice versa. Magnetite is 

 idiomorphic, but frequently possesses irregular outlines, owing to 

 the penetration of the crystals of plagioclase, augite, and apatite, 

 and the larger crystals are anhedrons, as they are moulded upon 

 the neighbouring laths of the plagioclase. The magnetite is 

 comparatively large and few, excepting its dendritic skeleton 

 crystals which are found abundantly in the specimen from Gio-o, 

 in company with devitrified glass. In the specimen, which is 

 wanting in dendritic magnetite, there are brown, biotite-like 

 lamellse usually in association with the hexahedral iron-ore. The 

 lamellse are anisotropic, and distinctly pleochroic, and the 

 mineral is conjectured to be ilmenite. 



It is of no small interest to note the presence of analcime. 

 It occurs sporadically rather in large patches in the cuneiform 

 spaces left by other crystals. It is generally fresh and colourless, 

 and isotropic, but often sho^YS the optical anomalies so common to 

 this mineral. At times, the analcime resolves into a dirty, iib- 

 rous natrolite (as in the left, lower margin in Fig. 0). The 



