CORRELATION WITH SIMLA SERIES. lOQ 
and Mr. Oldham, the latter of whom draws attention to the resemblance 
borne by the rock to the Blaini conglomeratic slate.^ 
During the recent survey of Spiti the present writer paid a con- 
siderable amount of attention to the question of the supposed resem- 
blance of these permiau conglomerates to the Blaini boulder-slates, 
and a detailed examination of the sections near Po and Pomarang, and 
also of the outcrops mentioned by McMahon and Oldham, has led 
him to the conclusion that the resemblance is only superficial. The 
Blaini boulder-slate is now generally regarded as of glacial origin, 
owing to the fact of its being composed of comparatively large boul- 
ders in a fine-grained, silty matrix, and the same characters have been 
claimed for the corfglomerate seen near Po and Dankhar. This latter 
rock occurs among a series of typical shallow-water deposits, consisting 
of quartzites, grits, gritty slates, conglomerates and occasional beds 
of fine-grained slate. The matrix of the conglomerate varies from 
a coarse grit to a gritty slate, corresponding in composition to a fine- 
grained, somewhat argillaceous sandstone : the rock has usually under- 
gone a considerable amount of crushing and shearing, thus being con- 
verted into a boulder-bearing slatC; the included fragments varying in 
size from small pebbles to boulders nearly a foot in diameter; the 
latter, however, are rare, the pebbles being as a rule about the size of 
the fist. 
Under the microscope, the rock appears to be an ordinary con- 
glomerate ; figs. I and 2 on Plate XVII represent sections of the matrix 
collected from the localities mentioned by Mr. Oldham and General 
McMahon. It will be seen that the specimen from Po is quite coarse 
and gritty, while that from below Dankhar is finer, but still only a 
gritty, arenaceous slate ; this represents the finest-grained matrix that 
the present writer has been able to find among the conglomerates of 
Spiti. In addition to the conglomerate, beds of fine-grained slate, 
presumably representing true silts,- are not uncommon in the series, 
but have never been found to contain pebbles or boulders, though 
» Records, G. S. I., vol. XXI, p. 151. 
( »09 ) 
