74 geology of the son valley, etc. 



In addition to these chemical changes the rocks everywhere 

 exhibit the effects of dynamical action which was, in fact, the 

 original cause of most of these chemical changes. 



All these rocks having been equally subjected to great compres- 

 sion and all of them altered in very much the same manner, it 

 follows that the differences in specific gravity which in fresh speci- 

 mens distinguish the more glassy basalts from the coarser porphy- 

 ries have become obliterated. Hence there is not much variation in 

 specific gravity, the mean density of all the specimens observed, 

 leaving out two rocks of perhaps less basic tendencies, is 2*98. 

 The extreme limits observed are within 2*9 to 3*1. 



It would be interesting to study a series illustrating their gradual 

 transformation from the unaltered rocks ; but such a collection 

 could not be obtained in the region which I visited, as all these 

 rocks are in advanced stages of metamorphism. In other parts of 

 India, however, the Bijawars have been much less disturbed, and 

 they furnish specimens which give some idea of appearance of these 

 rocks in their original condition. 



The collection in the Museum contains several rocks from 

 „ , , Bundelkhand which answer to this description. 



Rocks from Bundel- r 



kband. They have been alluded to by Mr. Holland 



(Records, Vol. XXX, page 37), and may be briefly referred to in the 

 present instance. Such are the specimens § and T 5 ^, ophitic dolerites, 

 consisting of labradorite, ordinary brown augite, and ilmenite, with 

 some biotite, micropegmatite and serpentinized olivine. In the hand- 

 specimen the rocks have the appearance of coarse basalts of the 

 freshest type without any of that green tinge which characterises the 

 metamorphosed material. The specific gravity of f is 3*04 ; while T % 

 consists of several fragments giving an average density of 3*09. With 

 the exception of the serpentinized olivine, all the minerals are abso- 

 lutely unaltered. The freshness of the specimens is surprising 

 considering their antiquity. In searching through the collection I 

 have succeeded, however, in obtaining some intermediate stages, by 

 no means a complete series, but yet sufficient to indicate that a 

 ( 74 ) 



