GENERAL CHARACTERS. 139 



There is, however, another subordinate mode of occurrence of 

 igneous rocks to be considered. In many of the limestone blocks thin 

 igneous veins, traversing the blocks from end to end, are to be seen. 

 These are instances of true intrusions. Wherever these veins are 

 present the limestones are much altered and marmorised. As a 

 rule ten or more veins are seen running parallel to each other at 

 regular intervals, a feature which is probably due to their following 

 bedding planes. Twice I met blocks with intrusions, which evidently 

 have been plicated, for they described narrow angles. 



The igneous rocks thus intruded resemble in macroscopic appear- 

 ance those surrounding the blocks. 



The explanation of these intrusive veins affords no difficulty. 

 They must have been formed while the limestones were still in situ, 

 although they had then already been acted upon by the igneous rocks. 

 Most likely therefore these limestones are derived from volcanic necks 

 and thus resemble in origin the volcanic blocks mentioned above. 



(b) The exotic blocks. 



Exotic blocks abound to such an extent that the number of those 

 exceeding 10 feet in diameter alone must be calculated to be many 

 hundreds while the smaller blocks are quite innumerable. The 

 volcanics of the Kiogarh high plateau especially are extremely rich 

 in exotic blocks. It would therefore be impossible to mark on the 

 map even the larger blocks separately. The course I followed was to 

 indicate those only which were found in any way remarkable, either 

 by their fossil contents, conspicuous forms, isolated position, etc. 

 Accumulations of large blocks, which contain little volcanic material — 

 such as occur in the Kiogarh heights (for instance Kiogarh No. 3) — 

 were marked as single limestone masses. The rest were left unmapped. 



The exotic blocks are of various lithological descriptions. Most 

 of them are grey or red limestones, but in places sandstone blocks 

 are common. Rarer types are blocks consisting of tuffs and shales. 



But these blocks being of sedimentary origin, lithological characters 



( '3 ) 



