EVIDENCES OF LOCAL EARTH-MOVEMENTS. 141 



supposed trap in the breccia. The strings and tongues of this black 

 material in microscopic structure do not resemble any known trap 

 or any substance which has solidified from thorough fusion. 



The heat which has fritted the mylonite in these brecciated 

 bands was probably produced by the friction during the process of 

 brecciation, for the peculiar structures show that the dislocation 

 must have been of a violent kind. Slow deformation of a rock 

 would crush the constituents throughout the mass, but strains more 

 quickly produced would result in dislocation along any narrow band, 

 and so in addition to this prima facie reason for concluding that the 

 dislocation was violent, the fact that its effects are confined to a 

 narrow band would account for the local rise of temperature and 

 consequent fritting of the mylonite. 



Apparent dislocation of trap-dykes. 

 The three exposures of dyke-rock described in a previous part 

 of this paper are so very similar in all their primary characters, that 

 one naturally examines the possibility of their having been originally 

 injected into one great fissure, and of having formed a single dyke 

 which subsequently became dislocated by earth-movements. In the 

 case of the two which are sufficiently extended to show the direction 

 of the fissure which they occupy, both dykes run N.-W. — S.-E., but 

 are nevertheless not in line with one another. An extension of the 

 line of the Karipatti dyke would meet the Shevaroys at a point near 

 Gundur, 3i miles from the S.-E. end of the Shevaroy dyke, which 

 would indicate, if these dykes were originally in line, the total 

 amount of dislocation which has occurred in the intermediate valley. 

 Careful search for the dyke has been made in the valley, but without 

 success. In fact the Shevaroy dyke, whilst extending continuously 

 from edge to edge of the Shevaroy mass, has not been found in the 

 low country at all, either to the N.-W. or to the S.-E (see Plate I). 



It is thus not unlikely that the Shevaroy mass is structurally 

 as well as petrologically distinct from the rocks of the country below 



( 39 ) 



