IGNEOUS ROCKS. 99 
augite, enstatite and ilmenite, all of which are accompanied by second- 
ary decomposition products, including green hornblende and serpentine 
after augite, bastite after enstatite, leucoxene and some sphene after 
ilmenite. The rock is intrusive in the cambrian slates and quartzites. 
About I mile to the north-east of Po, on the road to Thabo, a 
broad basic dyke cuts through the shales and 
Po : dolerite. . ^ i t-« • '-n^ ^ ■ 
quartzites of the ro series. 1 he rock is com- 
posed of plagioclase, near labradorite, a pale green, slightly pleochroic 
augite, apatite and ilmenite, with various secondary minerals, including 
chlorite, calcite and leucoxene. A very similar rock — which, however, 
contains also epidote — forms a dyke in the bills opposite Sumrd, and 
is seen again on the Sumrd La, while near Na numerous dykes 
of decomposed plagioclase-hornblende rock, with much chlorite, cut 
through the carboniferous beds. The dykes of Po, Sumra and Na 
are probably all offshoots from one matrix and differ merely in degree 
of alteration. 
In the Yituitse stream, between Sumra and Lari, a dyke — in part 
Actinolite schist ^ sheet — of actinolite-chlorite rock with decom- 
near Lari. posed felspar, some ilmenite, and sphene, probably 
represents a still further stage of decomposition. 
The above rocks have no characters of sufficient interest to demand' 
more detailed description ; it is quite certain, however, that they are 
intrusive, and not, as Stoliczka thought, contemporaneous flows inter- 
bedded with the slates and quartzites. It is necessary to emphasize 
this point, for the supposed existence of interbedded tiaps in beds 
regarded by Stoliczka as silurian has been employed as a means of 
correlating the volcanic beds of Kashmir and other areas with the palaeo- 
zoic systems of Spiti. 
Basic rocks of Rupshu. 
The traverse of Southern Rupshu made by the present writer was 
too rapid to permit of any detailed examination of the countless basic 
intrusions found throughout that district. At present it is only possible 
to say that there appear to be two distinct series of basic rocks— a 
H2 ( 99 ) 
