Monday, January 10, 2011

The Bridge over the River Beas

"Modern India with illustrations of the resources and capabilities of Hindustan", by Henry H Spry, M.D, published in the year 1838 has this remarkable story ( page 93)of how a suspension bridge over the River Beas was designed and planned by a Major Presgrave, and built entirely with material produced from the iron ore found closeby and using local labour.

Allow me to re-produce the story in its entirety.

"This suspension bridge has been constructed entirely out of the resources of the district, and by an amateur mechanic, who had never seen an iron suspension bridge in his life and yet we have an assurance from the visiting engineer for the northwestern provinces and Central India—Major Irvine, C.B., that he had seen nothing superior to it in England.

The undertaking was altogether an experimental one; for, as I have elsewhere mentioned, there are no roads in this part of the country of any extent, and, consequently, little or no traffic between remote places; its undertaking, therefore, originated in a desire to ascertain the capabilities of the materials and the workmen employed.

Saugor, and the districts in its neighbourhood, abound in iron ore; and the authorities were anxious to prove whether this valuable mineral could be manufactured into bars of a quality fit for bridges, and whether, at the same time, they could be fashioned by native smiths, who had never wrought, or even seen, iron of the required dimensions.

Major Presgrave, then assay-master at the Saugor mint, voluntarily gave his services to government on the occasion; and it was he alone who planned, entered on, and accomplished an undertaking which, considering the circumstances under which it was projected, must be esteemed a truly wonderful performance.

It forms a striking instance of genius, aided by the light of science, vanquishing apparently insurmountable obstacles. Engineers in Europe, accustomed to find everything provided for their wants, can scarcely conceive the difficulties which were encountered on the onset of this erection. None, save a master-mind, could have borne up against them. Not only was the business of builder and overseer, together with the subordinate trades of brick-maker, mason, carpenter, and iron manufacturer, to be added to his duties of architect and draughtsman, and that too in a climate in which a trifling exertion produces exhaustion, while incautious exposure will bring on fever and death; but he was also obliged to make the tools, and, ab initio, to teach the hands by which they were to be employed!

The foundation was laid in April, 1828, and the building completed and thrown open to the public in June, 1830. The iron of which it is formed is entirely the produce of the Nerbudda districts. When the bridge was projected, it was still in a state of ore in the mines, whence it had to be extracted, and smelted into small lumps, by the ordinary charcoal process of the country. The working of these crude, impure masses into good bars of the requisite dimensions and strength, proved to be a work of extreme difficulty and labour.

At the onset, two attempts were made before a rocky bottom could be found on which to lay the foundation. The banks of the river on either side are thirty-four feet high; the masonry was commenced six feet under the low-water level; the piers are forty-two feet high, the road-way being raised two feet above the ordinary surface of the country. The necessity of this precaution is apparent from the fact, that notwithstanding the height of the river banks, the freshes, during the season of the periodical rains, come down in such torrents that oftentimes the country is overflowed, and consequently, were not the platform of the bridge out of their reach very serious damage might be occasioned.

The bridge is 200 feet in span, between the points of suspension. The clear portion of the platform measures 190 feet by 11-1/2t. The tension of the bridge and chains, unloaded, is estimated, at either point of suspension, to be 95,632 tons; while, supposing the clear portion of the platform 190 feet by 11-1/2, or 2185 square feet, crowded with men at 691bs each superficial foot, the loaded bridge will have a weight of 120 tons; while the tension at each point of suspension will be 217,674 tons. This gives ten tons as the maximum strain that can be applied to the square inch of 'sectional area of iron. The general tension will, of course, be less than half that quantity.

A compact body of men, as a regiment of soldiers, for example, marching over a suspension bridge, is the severest test that can well be devised to prove the strength of the work, and since the completion of the Saugor suspension bridge, many corps of infantry have passed over it; effectually proving, had there been a doubt, which I believe there never was, in the mind of Major Presgrave on the subject, that the bars were sufficiently wrought to sustain this immense weight.

Every bar, before it was allowed to leave the yard, was tested by an apparatus for the purpose. It was made to bear a strain greater than its individual share would be when joined to its fellows, so that every precaution was taken that ingenuity could devise to insure success. Moreover, in the jointing of the bars, a method was pursued altogether new; but, in simplicity and efficiency, all judges who have examined it have decided to be, far superior to the plan commonly practised.

In the iron-work of the bridge there are twentyeight tons eleven hundred and eighty pounds of metal, which, in its finished state, cost about £2 12s. a hundred weight. The whole erection stood the Government in about £4800, exclusive of a present of £500 which Lord William Bentinck made to Colonel Presgrave, as a remuneration for his services, when his Lordship visited Saugor, in 1832-33; making the entire cost something more than £5000 sterling.

Notwithstanding the countless extra expenses incidental to a first undertaking of this kind, and the distance to which all the materials were obliged to be transported, from the work-yard at Saugor to the place of erection, the bridge has been pronounced to be cheaper than those in Calcutta constructed of English materials."

The narrator concludes the story with this eloquent praise.

"Here then we have a structure which, in elegance, in magnitude, and in durability, may vie with the most perfect specimens of the kind in civilized Europe. And yet fashioned out of the oxydized metal as it lies embedded in the bowels of the earth, by the rude hands of a class of artisans, by no means as expert as their countrymen in northern Hindustan, and the whole emanating from the genius and unremitting industry of one mastermind! Does not this speak volumes? Does it not satisfactorily show what India can do when her resources are properly drawn forth? And is it not a reproof to all who would seek alike to depreciate the country and the capabilities of her people? While an empire possesses engineers and artificers who are able to accomplish such a work as the Saugor iron suspension bridge, the infusion of capital is all that is required to render that country great among the civilized kingdoms of the world; and to this point must India arrive, if proper steps be taken to bring her capabilities into active exertion."

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