« PreviousContinue »
far the best crops of any land in the neighbourhood of the Jumna. Many of these deposits (which occur at every turn of the river) are several feet above its present highest levels ; these, however, the river by having deepened in its course since their formation, rather diminishes than increases by washing out those veins of sand, (parallels to the 2nd regular alluvial stratum of the D\’15.b general alluvium,) from one to six inches thick, which are invariably interstratified with this deposit : the more compact alluvial stratum above these veins being deprived of their support, separate and fall into the water in flakes, when, if the current is not too violent, the base of another deposit is formed, corresponding to the levels attainable by the river in its present bed, causing the upper surface of the united deposits, either to slope gradually towards the deep part of the channel, or the junction to be marked by a step or steep slope. All those, however, which are covered with only a few inches of water at the highest levels receive an additional deposit of sediment, which, however trifling, answers the purposes of the best manure. 2nd. Of the Rocks.
This term (as understood on the J umna) is applied to four distinct formations, namely—-let, superior sandstone; 2nd, volcanic; 3rd,isolated masses, the remains of beds of nodule kankar, and 4th, conglomerate rocks, composed of kankar and extraneous substances.
lst. Of the superior Sandstone. The only strata of this formation occur at intervals between the neighbourhoods of Bfirriari and
Dhowrie, two villages on the right bank of the river, and near Mhow, a village in the Bundelkhand.
Near Barriéri a great deal of good stone for building purposes, and of any dimensions, is quarried, (fig. 1. Pl. 3. spec. 1.) and sent to Allahabad. Very good stones are also procured from many parts of the bank near the above places, by removing two or three feet of loose earth or clay. It is fine grained, and very similar in colour and quality, to that procured from the neighbourhood of Bhurtpore. In fact I believe them to be portions of the same stratum, but am not
sufliciently acquainted with the geological features of Bundelkhand (the intervening tract) to make the assertion.
A portion of this stratum, thrown together in large masses by volcanic irruption, forms the curious little rocky island on which a Shiwala is so picturesquely perched in the centre of the river opposite the village of Dhowrie, about two days’ journey from Allahabad.
The other stratum occurs at Mhow only, and extends more than onethird cross the river. and is so friable and coarse as to be totally unfit for any useful purpose. Occupying its present situation, it
has caused infinite trouble, not only by the interruption a body of any sort must be to the navigation in such a place, but by the irregularities of its surface (forming the bed of the river), acting as receptacles for the moving kankar and other extraneous substances passing over it, in which have formed irregular masses of conglomerate rock occupying two-thirds of the whole width of the river. These, perhaps, at the time of their formation did not stand more than a few inches above the bed of the river, (the upper surface of the sandstone rock,) but the river deepening its bed in the course of ages has gradually worn away the sandstone, leaving the masses of conglomerate (on which it can make no impression), in the awkward and dangerous positions which they now occupy, with deep water all round them ; and although ome of the most dangerous have been removed, the passage down with a side wind is often impracticable to the clumsy boats used on the Jumna. It has this advantage over Karim Khan, (the worst pass in the river,) that the stream is not near so rapid. Those portions of this stratum which lie near the edge are exposed to the effects of the stream in a minor degree, and stand from one to five feet above the lowest levels, presenting peaks and heads of masses at irregular intervals over a space of about 500 by 200 yards. The exteriors of these are of a dirty green colour, which penetrates about one-eighth of an inch, and is, I imagine, caused by the action of the atmosphere. Under this coating, the natural colour of the stone appears, varying between every tinge of yellow and red, and pure white, which would indicate the presence of some portion of iron ; but one sight of the accompanying specimens will convince you, Sir, that but for the presence of some consolidating medium, the sand of itself would never resist the action of any stream. This consolidation occurs in the shape of numerous veins, from one-fourth to two inches in thickness, and from three inches to many feet in width, passing through it in every direction, and rendering it quite impervious to the stream with which it has to contend; and from the feeble attempts of which it is in fact defended by some masses of volcanic origin, which are described below. These veins (spec. 2) are either the deposit of some ferruginous spring, which has had a passage over the stratum, and on which the sand has from time to time accumulated, or is a lignitious lava; they occur in every position. horizontal, vertical, and at every possible angle with each of these : their outer edges are black, and bear a very high polish, produced by the action of the water. The fracture presents an appearance which would justify the conjecture of this substance having passed into the present position in a state of -fusion, as it encloses a substance within itself, having a vitrified appearance. The total absence too of iron within the bounds I am endeavouring to treat of, in any of the alluvial formations, and the intimate connexion existing between the sandstone, and substances of undoubted volcanic origin, strongly incline me to the opinion, that the heat necessary for the production of the latter, might have split the former, and that the interstices thus produced, have filled with the lava, (the present veins,) in a state of fusion. Another circumstance, confirmatory of this, is the fact of the sandstone being in a state of transition with the vitrified substances; but owing to the brittleness of the intermediate substance, (spec. d.) it was with the greatest difliculty I could procure the accompanying specimens. Of the Volcanic Racks.
These occur in two separate situations, namely, at Murka and Mhow. You will perceive, Sir, that the specimens from the former place, agree with Nos. 4, from the latter, although the shortest distance between these places cannot be less than 20 miles, perhaps more.
The mass at Murka, consisting of rough spheroidal blocks, varying from one by two, to three by five feet, lies on the right bank of the river ; their peculiar shape, appearance, and position, leads me to imagine, that they have been ejected in a partially vitrified state, and lodging in the water, the outer and angular parts have become slacked, and have been swept away by the stream, leaving these blocks, which, under these circumstances, are exactly similar to the core of badly burnt lime; in no other way can I account for their peculiar formation, which had it been produced by rolling, the same cause would have scattered them widely, but this has not been the case, as' they lie in a clearly defined mass, (fig. 2. Pl. XV.) and in this instance, have no other connexion with any other stratum than being superincumbent.
They correspond exactly with Nos. 4, from Mhow, both in the degree of vitrification, colour, texture, and every' thing but position; those at Mhow overlie, but are entirely detached from their bed, (sandstone,) and the same quantity is scattered over a greater space than at Murka. Their exterior is jet black. and so highly polished, that it is impossible to examine them for any length of time when the sun shines, the great light and heat they reflect during the day is peculiarly distressing to the vision. The interior is a mottled dark, and light red, one view of which is conclusive of its volcanic origin. (Specs. 3 and 4.)
Nos. 5, are specimens also from Mhow, the originals, (spec. 5,) occur in very considerable masses, having both sandstone and clay as a base, and standing above it from 1 to 20 feet; the largest of these