PETROGRAPHICAL NOTES. 6l 



of Agori jasper j it therefore immediately underlies the stage to 

 which this jasper belongs. It is very much finer-grained than T y F , 

 but otherwise resembles it in every way except for the much smaller 

 proportion of felspar. The felspar, moreover, differs from that of 

 the preceding rock in so far that it is all plagioclastic, 



If now we leave the rocks of the Agori stage and turn our atten- 

 tion to the upper division, we shall find that 



Other sandstones. , . . . . 



they contain a great many more or less sandy 

 rocks whose appearance differs greatly from that of the types we 

 have just described. The two rocks described from the northern 

 outcrop of the Agori band present all the characters of a quartzite 

 rendered very compact by the secondary growth of quartz. In the 

 higher series the sandstones remain much more friable because the 

 quartz-grains have not become cemented together by this secondary 

 extension, but are more or less separated from one another by 

 micaceous and earthy materials. 



The specimen T y T may be taken as a typical example of these 

 rocks. It was collected north of Baghaia or Bagra at a point where 

 the road crosses a small tributary of the Barwar river. The rock has 

 a dull grey colour in the hand-specimen and both quartz and 

 mica may be detected by the unaided eye. When examined under 

 the microscope it shows evidence of strain to a much greater 

 extent than the two sandstones described from the northern band 

 of the Agori stage. The quartz-grains though much smaller show 

 irregular extinction in a much greater degree ; they exhibit a 

 distinct elongation in the direction of schistosity and even show a 

 tendency to break off round the edges. It is probable that a great 

 deal of the finer-grained mosaic constituting the rock is therefore 

 of secondary origin. The quartzite though probably of later date 

 than the above described specimens from the Agori stage is yet much 

 more metamorphosed ; but this is in accordance with its situation 

 farther south, for the amount of disturbance in these rocks gradually 

 increases as we travel away from the northern boundary, the most 

 altered rocks being found at the extreme southern limit. 



( 61 ) 



