Plate XIV. 



Dislocation breccia. 

 The peculiar phenomenon described on pp. 198 — 202 under the name "trap- 

 shotten " gneiss was thought by older workers in South India to be due to the 

 injection of compact basic material into the gneisses. But microscopic examination 

 shows the black compact material to have the characters of mylonite, whilst the 

 disposition of these so-called " trap-shotten " bands in the field shows them to 

 coincide with lines of dislocation. The mylonite is extremely hard and brittle, and 

 probably has been highly heated, though not fused, by the heat produced during 

 the dislocation of the rocks; it has a composition similar to that of the rocks it 

 occurs in, and has none of the characters of basic, compact, trap rocks. 



