GEOLOGICAL SURVEY OF INDIA. 267 



Mr. Griesbach contributed to the February number of the 

 " Records" a small instalment of bis observations with the Afghan 

 Boundary Commission. The southern route taken to Herat crossed 

 the continuation of the tertiary and cretaceous formation previously 

 described by him at and west of Kandahar (" Memoirs," XVIII., 1), 

 the hippuritic limestone being very prominent with copious intrusions 

 of basic trap and syenitic granite. In the axial range of the Siah 

 Koh and Doshakk, south of the Herat valley, palaeozoic rocks make 

 their first appearance, as represented by a carboniferous Productus 

 limestone, dipping northwards towards the Hari Hud valley. The 

 Paropamisus range, north of the valley, seems to be largely made 

 up of a great plant-bearing series which Mr. Griesbach provisionally 

 parallels with the Indian Gondwana system, conjecturing that it 

 overlies the carboniferous productus-limestone. In notes of a 

 year's later date, published in the " Records," Mr. Griesbach adheres 

 to this general rock sequence, and describes its distribution in the 

 Binalat and other ranges of eastern Khorasan. 



The result of Mr. Oldham's observations in the Andamans is 

 published, with a map, in the " Records," and gives generally the 

 classification and distribution of the rocks, with a digest of all 

 previous explorations. Mr. La Touche was again despatched from 

 the Garo hills to take advantage of the topographical exploration 

 party to the head waters of the Dehing* on the extreme east frontier 

 of Assam. In that region the conditions are very unfavourable for 

 geological observations on account of the dense vegetation. It has, 

 however, been ascertained that the whole upper valley of the Dehing 

 is occupied by tertiary deposits, chiefly sandstones, while the actual 

 crest of the ridges to north and east are of crystalline rocks. Un- 

 fortunately, Mr. La Touche did not accompany the officers who 

 crossed the water-shed, consequently the opportunity of extending 

 the geological observations into the valley of the north-west branch 

 of the Irawadi. A good season's work was done by Mr. Jones in 

 mapping the whole area hitherto known as the Pench coal field, and 

 for some distance to the west in the direction of the Shahpur coal 

 field, on the south side of the Satpura Gondwana basin. The field 

 is, however, remote and inaccessible. Further light was shed on the 

 geology of the Lower Himalayan region, where the absence of fossil 

 guidance has always proved a perplexity, by the discovery by 



* See p. 79. 



