54 MEDLICOTT^ SHILLONG PLATEAU. 



below Kokon'on the norths to as far as Maplai; where I next observed 

 the rocksj under Tenrong, the Shillong* series is in place. In a direct 

 line along the Bogapani valley this granite must be ten miles wide. 



The relation of these great masses of granite to the Shillong 

 series puzzled me much. The commonly received special evidences 

 of intrusion are very obscurely developed ; and still less evidence is 

 there for the supposition that the deposits of the Shillong series 

 were accumulated around^ or upon, the granite. Although in this 

 latter case, one need not expect to find identifiable debris of the 

 granite in the sedimentaries, it is scarcely conceivable that such an 

 original symmetrical arrangement of the strata around the crystalline mass 

 could by any amount of subsequent contorting action be so utterly obliterat- 

 ed as we find it to be. This same absence of all symmetry in the arrangement 

 of the strata with reference to the foreign mass is also not in accordance 

 with at least one aspect of the supposition of subsequent intrusion — the 

 slow introduction of so great a mass would, one might think, impress 

 some regular structural feature upon the invaded stratified rocks contiguous 

 to it. Again, the more one renounced this aspect of intrusive action the 

 more would a priori considerations seem to require the presence of 

 direct and special evidences of a more energetic intrusion, in the form of 

 dykes and offshoots traversing the strata regardless of position ; but of 

 such I have not been able to find any. 



The granite is, on the whole, uniform in texture and composition. 

 As well as I can determine by simple inspection it contains — pale pink 

 orthoclase often in large crystals -, a much smaller proportion of very pale 

 greenish, striated felspar which I take to be oligoclase j an abundance of 

 hyaline quartz well disseminated, and a small proportion of dark green 

 or brown mica. The rock constantly affects a spheroidal structure. The 

 forms of these granitic areas are broad ; if elongated the width bears 

 a high proportion to the length j the ends are blunt. The boundary 

 is almost everywhere well defined, and there is ample opportunity for 



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