24 KOTO : XOTES ox THE GEOLOGY 



along tlie longest extension lies the axis of greatest elasticity, 

 and there are tens of thonsands of laths visible in microscope 

 slides, with bnt a few tabular sections. Symmetrically opposite 

 extinctions make the maximum angles of 23° to 25° with the 

 suture of lamellae, Microlithic sections twinned on the albite 

 type extinguish at the angles from 0° to 26°, with reference to 

 the longer dimension. According to Michel-Levy, labradorite 

 and albite have similar optical deportment, but as they do not 

 usually come together, and as we are dealing now with a basic 

 rock, the nature of the microlite should be considered to aj)proach 

 that of an acidic labradorite. In a few slides, the poles of 

 the laths resolve themselves into a number of prisms, and such 

 fine slender needles are scattered through the whole groundmass. 



AÜGITE. 



Augite, so says Morozewicz^^ belongs to one of the * t'er- 

 hangniss'vollen minerals. It does not obey Fouque and M. -Levy's 

 rule of crystallisation of silicates in the reversed order of 

 fusibility, nor Rosenbusch's scheme of crystallisation according 

 to acidity. It is rather subjected to the influence of masses, i.e. 

 a degree of saturation under certain temperature and pressure. 

 Under such circumstances, augite may form crystals before 

 plagioclases, and at other times, just the reverse may occur, 

 while in the third case they may individualise at the same time. 

 According to the priority of secretion of either of the two 

 minerals, in other words, the relative idiomorphism of one to 



]) 'Experimentelle Untersuchungen] uel>er die Eiklung der Minerale im Magma.' 

 Tschermak'.^ Milth., Bd. XVIII., S. 84. 



