MEMOIRS 
OF 
THE GEOLOGICAL SURVEY OF INDIA. 
The Geology of Spiti, with parts of Bashahr 
AND Rupshu, by H. H. Hayden, B.A., B.E., F.G.S., 
Deputy Super mi endent, Geological Survey of India. 
INTRODUCTION. 
Our knowledge of the geology of that part of the higher Himi- 
layan ranges which lies to the west of the Nepal frontier has been 
derived chiefly from the examination of three distinct areas, namely, 
the Kumaon and Garhwal Himalayas on the east, Kashmir with 
Ladakh on the west, and Spiti, lying between these two. This three- 
fold partitioning is not due to any geological or stratigraphical 
peculiarities of the respective subdivisions, but merely to their physi- 
cal conformation, each area being accessible from one or more routes 
which are more or less central to it, but do not give access to the 
others, while the passage from the central area, Spiti, to those lying 
on either side is a matter involving considerable time and difficulty. 
The inevitable consequence of these conditions is a lack of homo- 
geneity in the geological results, a lack still further enhanced by the 
fact that, except with regard to the lower trias, no two areas had until 
quite recently been examined in any detail, nor, with a few excep- 
tions, even visited, by one and the same observer. 
Naturally, it is to the central, or Spiti, area that we look for the 
means of correlating what knowledge we have of the neighbouring 
divisions; but this is a matter of no small difficulty. The eastern 
B ( , ) 
