30 MALLET, VINDIIYAN SERIES. 



In Bundelkund they tliin out westwards and become extinct north of 

 Saugor. Their western overlap is thus established on both north and 

 south ; their extreme length from Rotasgurh to where last seen in Bun- 

 delkund being 350 miles. 



Tor more than one reason the lower Vindhyans do not admit of 

 the same accuracy of classification as the upper. The sub-divisions which 

 exist in any one section are not all to be found in another at a consider- 

 able distance ; the difierence arising partly from a tendency they have 

 in some cases to die out, and in others to lateral change in lithological 

 character. The much greater disturbance which the lower series has 

 undergone, the absence of such clearly defined physical features, con'es- 

 ponding to the geological lines, as are met with amongst the upper, and 

 the want of good maps on which to record one's observationSj all combine 

 to render a detaileji classification of the lower Vindhyans applicable to their 

 whole extent, a work requiring more time than could justly be given to it 

 by the survey. The division of the series given at page 28 is that which 

 is found to obtain in the eastern area. Some members can be traced 

 almost continuously all along, but the identification of others in the west 

 with those in the east is to a certain extent conjectural. The relative 

 importance of the different members is very different. Some are constant 

 and preserve a tolerably uniform thickness for long distances, while 

 others are only to be found in certain localities, even there sometimes 

 occupying a subordinate position. The lowest beds are less constant 

 than those higher up, a reason for which suggests itself in the original 

 conditions of deposition. Tlie floor on which the series was first laid down 

 was a most uneven one, formed by the hills and valleys which marked the 

 alternating hard and soft highly inclined beds of the older slate series. 

 After the first Vindhyan strata had filled up such depressions, the more 

 even floor then produced naturally led to greater evenness of stratifica- 

 tion in the succeeding beds. 



( ^O ) 



