well-defined structure. 

 Some augite was pro- 

 bably also present. 

 The felspar - pheno - 

 crysts consist of acid, 

 oligoclase, twinned ac- 

 cording to the albite 

 and Carlsbad laws, 

 and giving the 

 characteristic low 

 maximum extinction- 

 angles measured onto 

 the twin lamellae. 

 The orthoclase is most 

 usually untwinned. 

 Both felspars are more 

 or less decomposed, 

 giving rise to secon- 

 dary quartz and seri- 

 citic material. 



The hornblende no 

 longer exists as such, 

 but is represented by 

 pseudomorphs in pale- 

 green chlorite with a 

 low double-refraction. 

 These pseudomorphs 

 are beautifully shaped, 

 having the angles and 

 cleavages of the ori- 

 ginal mineral well- 

 preserved. The clea- 

 vages are often marked 

 by little stri ngs of iron- 

 ores, as also in many 

 cases is the border of 

 the crystal. 



V. Structure, Fold- 

 ing, and Faulting 

 of the District. 



The structure of the 

 district is one of great 

 complexity, and there 

 are many of the pro- 

 blems that it has pre- 

 sented that we do not 

 pretend to have sol ved ; 

 some few salient 

 points, however, may 

 be regarded as certain. 



The general struc- 

 ture of the district is 



