640 ANCIENT FLUVIATILE DEPOSITS 



of this section the rivers, as in the case of the ' Blue ' and 

 ' White ' Niles, have intersected horizontal beds of argillaceous 

 or arenaceous travertine, or banks of aggregated nodular 

 kankar, which frequently form dangerous subaqueous reefs 

 or bars, obstructing boat-navigation. The Government of 

 India undertook in 1828 a series of operations, which ex- 

 tended over seven or eight years, for the removal of these 

 and other obstacles from the bed of the Jumna, in which 

 they are most prevalent. These were conducted by highly 

 instructed officers of the Bengal Engineers, one of whom, 

 Captain Edward Smith, published an account 1 of the most 

 striking facts which were observed on the occasion between 

 Agra and Allahabad. The upper half of the section, consist- 

 ing of beds of sand and clay, contained throughout, in more 

 or less abundance, the impure calcareous concretions called 

 nodular kankar. Near the base of the lower half these 

 calcareous deposits were developed in much greater force, 

 sometimes forming strata of rock kankar, from 1§ foot to 2 

 feet thick, with a thinner bed of clay interposed. At one 

 point, Burlot, below the junction of the Chambal river, where 

 the bank is precipitous and 100 feet high, a stratum of rock 

 kankar, in the form of a granular concrete 2 feet thick, was 

 observed 60 feet above the lowest level of the stream. But 

 the most ordinary condition of the material is the concre- 

 tionary, in the form of nodular botryoidal stalactite or ramified 

 kankar. In some places the concretions, closely compacted 

 and connected by veins, are disposed in horizontal strata in 

 clay, at 10 or 12 feet above the level of the stream ; in others 

 the kankar presents itself in vertical seams in the scarped 

 front of the bank, or it ramifies in every direction through 

 the clay, literally lacing it together ; and occasionally ancient 

 surfaces of sun-cracked clay, where denuded, are seen with 

 the fissures filled with septarian plates of the same material. 

 At one point, Kareern-khan, slab-kankar, used for building- 

 purposes, and consisting of fine sand solidified by carbonate 

 of lime, is quarried at shallow depths from under the bed of 

 the river. Captain Smith (from whose memoir the above 

 particulars are for the most part drawn) has given an ex- 

 cellent series of highly instructive sketches, showing the 

 various modes in which the kankar occurs along the banks 

 of the Jumna. 



2. Mammalian Fossils. — Fluviatile shells were either ex- 

 tremely rare, or they escaped the notice of individuals who 

 were not familiar with this walk of observation. Only two 

 instances are recorded — one an open TJnio, embedded in a 



1 Journ. Asiat. Soc. Bengal, vol. ii. p. 622 (1833). 



