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require a mass in superficial area equal to twenty-eight feet by eighteen, to a depth say of from six to ten feet, which would be quite sufficient, even if the mass rested on sand. There is no reason why, by piercing this block with cylinders, the whole might not be lowered, and a foundation obtained of infinitely greater security, and certainly not at ⚫ greater expense, than any of the methods now adopted. The great advantage however of this plan over others, is its simplicity; all the apparatus, machinery, &c. of pileing are thrown aside; a few carpenters procurable at every village, and masons to be had without difficulty, with some Chah-kuns to sink the mass, are all that is required.
Where stone in slabs is to be procured, a method is adopted by the natives of forming what they call kothis, that is to say a caisson without a bottom. The stones are clamped together, as shewn in Fig. 3. Pl. 3, by wooden clamps; these boxes are undersunk in the same way as the cylinder, but the form is inconvenient, and the difficulty of sinking them greater than either the cylinder or the block above described. The circular form as regards friction alone, offers a much smaller surface than the square; but the square block of Colonel Colvin has great weight to assist its descent, which the stone kothi has not. In the foundations of the bridge over the Caramnassa river, laid down by Nana Farnavis, these kothis were extensively used. These foundations when laid bare for the ulterior operations appear to have extended across the bed of the river on a width of sixty feet, the kothis, which were fifteen feet square, being placed close together, and sunk through sand to a depth of twenty feet. The reader is however referred to Vol. 3. of the Gleanings in Science, in which Mr. James Prinsep has given a most interesting detail of the Caramnassa bridge operations. I may however remark that the kothis in question after being sunk are filled with grouting, or a mixture of lime, kunkur, &c. (concrete) forming an artificial conglomerate, upon which the superstructure is raised. Mr. Prinsep uses the word dhoka, in this part of India ghutta is the term usually applied to this species of material. The jamwat corresponds with the neemchuk of the northern Doab.
Another species of kothi, which is also used not only in foundations but in village wells, consists of frames of wood joined together at the angles, as represented in Fig. 4. Pl. 3; this from the want of weight is still more difficult to sink than the one before described; it is however convenient where wood is plentiful, and the soil to be pierced of a light description; they are undersunk precisely in the same way as the common cylinder. In village wells, when the kothi is from four to five feet square and the thickness or scantling of the wood used four or five
riably filled the cylinder with large masses of kunkur, or vitrified brick, without cement of any description, on the principle, that if the stratum upon which the cylinder rested was at all acted upon or undermined, the masses of loose material would sink and occupy the space caused by the action of the water below; in fact the hollow cylinders are quite sufficient to support the superstructure placed upon them, the internal space may therefore be well occupied by any means to counteract danger from the vagaries of the stream.
The varieties of lime procurable between the Himalayas and Delhi are peculiarly favourable to hydraulic works. The beds of the rivers which drain the valley of Deyra, situated between the parent mountains and the Siwaliks, are loaded with boulders of lime rock; the shingle strata of the Siwaliks themselves contain also a plentiful supply; these, with the main outlets of the Jumna and Ganges provide lime for all the upper portion of this Doab. The boulders are collected and either burnt on the spot, or carried to the works; in the former instance the cost of the material from the Hills to points between them and the town of Saharunpoor averages as follows::
Cost 100 maunds at the Kiln from 8 to 10 Rs. say,
an anna → bullock load
Although this lime is in many cases pure, i. e. crystalline carbonate without admixture-and by selecting the boulders previously to burning may be obtained sufficiently pure for the whitest stucco, or white-wash-the article from the kilns is much adulterated with clays and metallic oxydes, arising from the varieties of lime rock which are thrown into the beds of the rivers. With the use of soorkhee therefore (or pounded brick) this lime makes an admirable watercement. In wells and foundations I have generally used it in the following proportions:
2 parts Soorkhee
1 ditto Lime, or
5 maunds, or 400 lbs. of Soorkhee
12 maunds, or 140 lbs. of Stone Lime
mixed well together in a mortar mill before it is used. Above the level of the water I have found it advisable to reduce the quantity of soorkhee; the cement in this case consists of
1 parts of Soorkhee, or 33 maunds
1 ditto of Lime, or 1 maunds.
The lime in fact is so good, that where well burnt bricks are used, bad masonry is entirely out of the question; the builder cannot help himself, and for this portion of his duty deserves no sort of credit whatever.
This stone lime is used universally on the Doab Canal from the point where it leaves the Jumna to Rampoor, a town twelve miles south of Saharunpoor; from this the marles and kunkur limes of the districts come into use, although the stone lime is brought into requisition on a smaller scale for arch-work as well as parapets; and in plaistering masonry works it is solely used.
The marle, or earth lime as it is usually called, is in much greater abundance on this line than kunkur. When extracted from the quarries or pits, it is perfectly soft and friable, in which state it is kneaded up into round balls about two or three inches in diameter, which are placed in the sun to dry, previously to their being burnt in the kiln. The marles differ very much in quality, but all of them make an admirable water cement. That from Jussool, a village on the Khadir of the Hindun river is the most approved of, and is delivered on the works within a circle of ten and fifteen miles at about twelve Rupees per 100 maunds. These marles are full of fresh water shells of species now existing in all the tanks, jheels, and rivers of the country; those of Melania, Lymnaea, and Planorbis being in the greatest abundance.
The kunkur limes are more numerous in the southern districts of the Canal, they also make a good water cement, but contain no remains of fresh water exuviæ.
Near a village called Hursoroo, twenty-five miles to the south-west of Delhi, a very superior kunkur lime is procured-the formation itself is intermediate between kunkur and marle, but the position of the quarries from which it is excavated is similar to that in which all this material is procured, in a low tract of country, the site in all probability of a lake or jheel now filled up.* The same fresh water shells as are found in the marles to the eastward of the Jumna, are very numerous in the Hursoroo lime. It is exported in large blocks, and is sold in Delhi at from twelve to fifteen Rupees per 100 maunds. The cost after burning varies from twenty five to thirty Rupees per 100. This lime for a water cement is very far superior to any lime that I have met with. When calcined it is of a very light color, and
* Hursoroo is situated on a nullah which rises in the small hills near the Kotub Miner, and flows into the southwest end of the Furnuknuggur jheel. The town of Hursoroo, or as it is more commonly called Hursoroo ghurree, is about two miles from the jheel.
might be mistaken for the stone lime of the Northern Division. In the locks and works on the Doab Canal, appended to them at Shukulpoor, Sikrani, and Jaoli, in the southern district opposite Delhi, nothing but Hursoroo in the following proportions has been used in the superstructure,
and in the neighbourhood of Delhi the use of pounded brick, or soorkhee, has been almost entirely superseded by that of Bujree.t
The sand stone, which is an attendant upon the great Quartzoze formation of the ridge upon which Tughlukabad, the Kotub Minar, and old and new Delhi stand, varies from compact and crystalline, to a loose and friable rock; in this latter case it consists of an agglutination of minute angular fragments of quartz, with, in some cases, a red oxyde of iron in such abundance as to give the strata quite a peculiar character; in other cases the oxyde is wanting, and this friable rock is of a light color. For roads and other purposes these varieties of the sand stone are much in request, and amongst the natives obtain the name of Bujree. Nothing could be a better substitute for soorkhee, than the substance in question. The presence of the iron oxyde is in every way favorable to its value in hydraulic works, and the sharpness of the particle of which it is composed renders it an admirable mixture with lime for plaister or stucco. In this form it stands the effect of the climate much better than soorkhee or river sand. In the proportion of one part of Hursoroo lime to one part of bujree, mortar laid on with a float, as is used in sand, may be considered very far superior to it, and with a much better appearance than that practised by the natives, under the tedious process of beating with the thappa. This bujree is now universally used on the Doab Canal works, at all points at which it can be delivered under eight rupees per 100 maunds, this being the maximum rate of
The following is the detail of proportions used in the cement at these works, and as they were built in 1834-35, a sufficient time has elapsed to judge of the durability of the masonry, no repair of any description having taken place up to this period.
1 part. 2
...... ...... ....
†This has I believe been the case in the Delhi works for many years.