MANUAL OP THE NILAGIRl DISTRICT. 



87 



the rock shows a tendency to split off in enormous slabs slightly CHAP. v. 

 curved to the form of the hill side/^ The probable cause o£ these n 



. ^ (jrEOLOGY AND 



sphts IS the heat of the sun, which makes the surface layers Mineralogy. 

 expand rapidly and then separate from the cooler rock beneath. ^, TT 

 After heavy rain the decomposing mass, being saturated with 

 water, frequently breaks oif from the main rock and rushes down, 

 scattering the embedded boulders over the valley below. The 

 mark of such landslips may be observed along the Doddabetta 

 slopes forming the north-east side of the Kaity valley. 



Mr. Blandford draws attention to the banded structure of the Banded 

 gneiss, which contains much hornblende, about Paikare and structure of 

 Mlikarte. The bands protrude from the hill-side and always run 



HARD BAND&IN GNEISS, NEAR NEDDIWUTTUM, 



in the direction of the foliation. Traces of this banded structure 

 also appear in the hills around Ootacamand, but it is rarely 

 possible to trace them to any distance, as they " either become 

 lenticular or break up and die away in the mass.'' He then 

 refers to a remarkable limestone formation in Coimbatore ^ exhibit- 

 bg the banded structure of these rocks more clearly. The lime- 

 Istone and the gneiss run in alternate bands. " The regularity 

 ind continuity of this rock for a distance of six miles and proba- 

 bly even more render it difficult " he writes, " to believe that it 

 pan be other than a really metamorphosed band of sedimentary 



Series. 



Notice, Madras Journal of Lite'>-atih'>-e and Science, "Vol. Ill, No. V, N§w 



