88 MANUAL OF THE NILAGIRI DISTRICT. 



CHAP. V. rocks^ and afford the strongest evidence of such an origin that has 

 Geolog^ and y^^ ^^®^ obtained in this part of India.'' 

 Mineralogy. 



FIC.I/I- TMIH ALTERNATIONS OF LIMESTONE AND CNEISS, WEATHERED,- NfAR COIMHATOOR. 



Intruded 

 rocks. 



Dislocations. 



Three 

 systems of 

 faults. 



As already mentioned no granite is found on the hills^ and the 

 other rocks which were regarded by Dr. Benza as of igneous 

 origin are now shown to be foliated. A few small dykes, however, 

 of rocks which are undoubtedly trap occur. One will be observed 

 north of the Paikare road near Ootacamand and another on the 

 northern slope of Snowdon, " about 200 yards from the summit, 

 and again to the north-west in the_bed of a small water-course 

 on the western side of the valley, and in both cases consists of 

 several small parallel dykes, varying from two to ten inches in 

 width, and consisting of a tough compact basaltic rock." These 

 dykes run north-west, or nearly at right angles to the foliation of 

 the gneiss. Trap dykes also appear at the south-west extremity 

 of the district near Sisapara. Mr. Blandford's paper contains a 

 minute description of these dykes by his assistant, Mr. King. 

 As regards the age of the trap dykes no evidence, Mr. Bland- 

 ford observes, is forthcoming, consequently " it is impossible to 

 say whether or not they are connected with the great outbreak 

 of the Deckan." Similar dykes, however, occur in Mysore. 



Mr. Blandford's remarks on these subjects seem to me too 

 valuable to be curtailed. After observing that ample evidence 

 of the dislocations which have occurred is forthcoming in the 

 physical features of the surface, and to some extent in the 

 presence of mineral veins, he proceeds : — 



" There are three principal systems of faulting, two of them 

 probably synchronous and at right angles to each other, being 

 those which coincide with the lines of the Eastern and Western 

 Ghats respectively, and a third, probably sub.^^equent to the above, 

 and contemporaneous with the final upheaval of the Neelgherry 

 plateau. 



