90 Address. [Feb. 



r Upper Jaonsdr. 

 JAONSAR SYSTEM. < Jaonsdr Quartzite. 



V. Lower Jaonsdr. 

 1 Central Gneiss.' 

 In discussing the correlation of these systems with those of Stoliczka, 

 Lydekker, Waagen, and Wynne, in Spiti, Kashmir and the Panjab, as 

 also the Yindhyans in Peninsular India : the conclusion is arrived at 

 that the Central Gneiss is presumably of Archaean age ; that the Jaonsar 

 system may be equivalent to the Vindhyan in the Peninsular area, this 

 correlation tending to give both systems an age corresponding at the 

 latest to part of the Silurian system of Europe. No equivalent, however, 

 can be found among the fossiliferous beds of the Central Himalayas for 

 the Deoban limestone. The Carbonaceous system, in correlation with 

 Lydekker's Zanshars and Panjals in Kashmir, and Stoliczka's Ruling of 

 Spiti, is considered to have been deposited during the latter end of the 

 Palaeozoic period, and that it corresponds to part, if not the whole, of 

 the Carboniferous and Permian eras. The Krol limestone is then con- 

 sidered as probably represented by part, which part cannot be deter- 

 mined, of the limestones which extend from Lower Trias to Lias in Spiti 

 and Kashmir. 



The attention of the officers of the Geological Survey of India ap- 

 pears to have been specially directed during the year to the elucidation 

 and working out of several important questions connected with econo- 

 mic Geology. 



As regards the economic importance of the TJhdrivdr series, further 

 exploration points to an increased promise of their value, in the recog- 

 nition by the Survey of an extensive and promising gold-field in the 

 Raichur Doab of the Nizam's Dominions. 



An interesting question has been opened up, quite lately, regarding 

 the occurrence of diamonds in the Madras Presidency, otherwise than in 

 what has been hitherto considered the proper diamond- bearing 

 sandstone (Banaganpilis) of the Karnul formation. A few diamonds, 

 one of them of considerable value, had been found at Wajra Kurur, where 

 there is no trace now of the Banaganpilli beds from which they might 

 have been derived : and it is supposed, with some show of plausibility, 

 that the gems may have come from a " neck " of igneous or volcanic 

 rock occurring there, which bears some resemblance to the " blue " of 

 the Cape diamond-fields. It is doubted by the Survey whether the 

 diamonds can be so derived, preference being given to the view that 

 they occur in a remnant of the debris — present surface soils and gravels 

 *— of some pre-existing diamondiferons portion of this " neck " rock 

 which had passed through carbonaceous deposits long since denuded 

 from the face of the country. 



