1835.] On the Strata of the Dudb Alluvium, 261 



IV. On the Strata of the Jumna Alluvium, as exemplified in the Rocks 



and Shoals lately removed from the bed of the river ; and of the sites 



of the Fossil Bones discovered therein. By Serjeant Edmund Dean. 

 [The Specimens alluded to are deposited in the Society's museum.] 



It has always been a matter of speculation with me, since my first 

 acquaintance with the Jumna, that presenting the obstacles to naviga- 

 tion, which it, undoubtedly, does at the present day, after seven years' 

 application of great talent, and a very considerable expenditure, what 

 a gigantic work it must have appeared at its commencement. Expe- 

 rience, however, and a careful research have confirmed me in the opi- 

 nion, that many of these impediments in one shape or another, were 

 then, and are now, not only such as, their existence once known, could 

 easilv be removed, but there is every probability of some of the most 

 dangerous of them being at this instant in a state of active formation 

 and increase. 



Taking a general view of the whole, as they occur between Agra 

 and Allahabad, I have found it convenient to class the obstacles most 

 to be dreaded by navigators, as follows : 



1st, Clay-banks or shoals ; 2nd, Rocks ; 3rd, Kankar shoals, and 

 4th, Sunken trees. This classification is adopted with reference to 

 the supposed degree of danger to the navigation that may be attached 

 to each, a detailed description of which I have endeavoured to ar- 

 range in this order. 



The grand and perfect section of the Delta of the Jumna and Gan- 

 ges, (or I should rather say, from experience lately gained to the west- 

 ward, of the immense generul alluvium of Hindustan, opened by the 

 channel of the former,) presents a regular alternating stratification of 

 the different modifications of which the general Dtiab alluvium is 

 formed ; which consists (as far as the section has allowed me to exa- 

 mine), of five distinct strata, interspersed with imbedded substances 

 which from their irregular growth, positions, and occurrence, cannot 

 be classed among the more regular strata. The regular strata occur 

 as follows, namely, 1st, Superior sandstone ; 2nd, Shale, and 3rd, 

 4th, and 5th, Alluvial, (fig. 1. PI. XIII.) 



Only two strata of the superior sandstone occur within the above 

 bounds that I am aware of. The elevated positions of both decidedly 

 have been produced by volcanic irruption, and will be described under 

 the head of rocks. 



The Shale which approaches nearest to d, var. of A. in the first division 

 of McCulloch's synopsis, described as passing into clav, appears very 

 seldom. Note. The specimens marked " y, 1, 2, and 3," all stand the 



