382 Reports & Proceedings — Mineralogical Society. 



thephyllites and schists, notably near the granite junction; (4) the 

 granitic intrusions traversing the limestone and forming an important 

 source of ore. 



The angularity of the boulders and of the tin-ore in some of these 

 clays is due (1) to weathering in situ of the phyllites and schists, 

 which then sink on the dissolving limestone underneath ; (2) to soil 

 creep effecting the same result; (3) to the breaking-up of the much 

 weathered cassiterite-bearing boulders and pebbles in the alluvium. 



Over 90 per cent of the ore worked in the whole of the Kinta 

 District is obtained from mines situated at less than a mile from 

 granite or from granitic intrusions. 



Mineralogical Society. 



Junelb, 1915.— Dr. A. E. H. Tutton, F.P.S., President, in the Chair. 



G. M. Davies : Detrital Andalusite in Cretaceous and Eocene Sands. 

 Detrital andalusite is not confined to Pliocene and later deposits as 

 was formerly supposed, but is a frequent constituent throughout the 

 Cretaceous and Eocene beds of the South-East of England. In the 

 Lower Cretaceous beds it is still perfectly fresh, and shows no signs of 

 instability under the influence of meteoric water. — J. P. N. Green : 

 The Garnets and Streaky Pocks of the English Lake District. Certain 

 peculiar rocks occurring in the Lake District are characterized by 

 almandine garnets and parallel streaks of secondary minerals. The 

 capricious distribution of the garnets in diverse rock-types was 

 considered to exclude originality, and thermal or dynamic alterations 

 were shown to be inadequate. Circulating solutions under pressure 

 during the solfataric stage of the Borrowdale episode were suggested 

 as the agent, and illustrations were given of the replacement of 

 felspar by garnet in Lake District rocks. The same origin was 

 assigned to the streaky infiltrations which frequently contain pyrites 

 or garnet. — Dr. S. Kozu : On the errors in the angle of the optic 

 axes resulting from those of the principal refractive indices determined 

 by total reflection. The indices so found are correct within , 0002 

 for sodium light. Assuming the error to be only half this, the 

 extreme values of the angle are for anorthite 76° 8'6' and 79° 21*8', 

 for albite 76° 14-1' and 80° 46-9', and adularia 56° 16-9' and 

 65° 56-9'. — Dr. S. Kozu: The influence of Temperature on the Optic 

 Axial Angle of Sanidine from the Eifel. Pockels has shown that in 

 those rhombic crystals in which the axial angle varies considerably 

 in the neighbourhood of zero the relations between the angle and the 

 temperature is represented by a parabola. Sanidine from the Eifel 

 very nearly approaches the conditions of a rhombic crystal. The 

 values of 2E were determined for seven different wave-lengths. 

 The plotted curves were found to accord with Pockels' statement ; 

 further, the complex curves for the various wave-lengths were 

 identical. — Dr. G. T. Prior : The Meteoric Stones of Warbreccan, 

 Queensland. Three stones, weighing respectively about 69, 64, and 

 1 lb., were known to the natives of Central Queensland before 1904, 

 and their fall was probably seen. They were acquired by the British 

 Museum in 1905. They are white-veined chrondites, and in chemical 



