10,5 HOLLAND: SIVAMALAI SERIES. 



of hornblende-elseolite-syenite (No. 11,470) from Sivamalai. Such 



F*g> 3-~~ Hornblende-elaolite-syenite shewing glomeror plasmatic hornbUndic 

 patches distorted\to produce gneissose structure. No. 11,470 {Natural 

 size), W. face of Sivamalai. 



hornblendic patches are on a small scale strictly analogous to 

 schlieren, and illustrate the formation of gneissose structures, and, 

 by further development, banding through distortion of a schlierig 

 rock-mass. This explanation, which I have already applied to the 

 charnockite series, 1 was suggested ten years ago by Bonney and 

 McMahon as the cause of banding in the granulitic group of the 

 Lizard in Cornwall, and was proposed by them as a sufficient explan- 

 ation of banding in many Archaean gneisses. 2 The same idea has 

 been more than once since applied, especially to banded basic rocks. 



1 Mem. Geol. Surv. Ind., XXVIII, 1900, 221. 



2 Bonney and McMahon, " Results of an examination of the crystalline rocks 

 of the Lizard district." Quart. Journ. Geol. Soc } XLV1I, 1891, 478, 



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