have carried the art with them into every iron making country in Europe, as well as to India and America.

Nothing, it is said, succeeds like success; and no sooner had Mr. Bessemer demonstrated the certainty, the celerity, and the cheapness of his process, as was abundantly proved by the article itself, and the price at which he sold it, than many of the great iron-manufacturers followed his example, and the production of Bessemer steel is now a large and rapidly increasing branch of English industry. In September last there were in- actual operation in Great Britain seventeen extensive Bessemer steel works, and there were then erected, or in course of erection, no fewer than sixty converting vessels, capable of producing 6000 tons of steel weekly, or equal to fifteen times the entire production of cast steel in Great Britain before the introduction of the

new process. The average price of the steel so manufactured being at least 207. less per ton than the previous average price of the metal, there is thus shown a saving of not less than 6,240,000l. per annum in this country alone, even in the present comparatively infant state of this important manufacture.

Bessemer steel is calculated to be of especial value in all engineering work where lightness and strength are required, such as the framing of marine engines, screw propellers, the cylinders of hydraulic presses, and all kinds of machinery. It is equally well calculated for light girder-bridges of large span, and for the plating of ships; much less weight of metal being required, at the same time that a greater degree of strength can be given to all parts subjected to heavy strains. One firm in Liverpool has already constructed 31,000 tons of shipping wholly or partially of Bessemer steel. But probably the most important uses of the metal consist in its application to railway purposes, where great strength is required to meet the tremendous strains arising from the high speeds at which railway traffic of all kinds is now conducted.

The first rails laid down between the pits and the coal staiths in the North were of wood. All that they were required to do was merely to bear the load of a chaldron waggon, drawn at slow speed by a horse; and they were sufficient for the purpose. To protect them in a measure from the jolting occasioned by the irregularities in the road, as well as from the effects of increasing traffic and heavier loads, the wooden rails were in some cases tipped with thin plates of iron nailed along their upper surface. Cast-iron rails were next introduced, and continued in general use in the coal districts until the introduction of the locomotive engine. Even after the Killingworth locomotive had been at work for two years,

we

we find George Stephenson, in conjunction with William Losh, taking out a patent for an improved form of cast-iron rail; and when the Stockton and Darlington line was constructed and opened in 1825, half the rails laid down were of that sort, But the material was found altogether inadequate to bear the increasing weights and strains to which it was subjected. The locomotive, when running even at a moderate speed over the cast-iron rails, champed them up like so much pottery ware; and the constant breakages and interruptions to the traffic which their failure occasioned shortly led to their total disuse, and the substitution of rails of malleable iron.

The first wrought-iron rails laid down were only 25 lbs. to the yard; but they were soon found too light for the loads they had to carry. When George Stephenson was examined by Mr. (afterwards Baron) Alderson, before the Committee on the Liverpool and Manchester Railway Bill, he was taken to task about the weakness of the Hetton road, and the danger of travelling by railway, on the assumption of trains being run at the dangerous, but then hypothetical, speed of twelve miles an hour. The witness was asked-Do not wrought-iron rails bend,-take Hetton colliery for instance?'-'They are wrought iron, but they are weak rails.' 'Do you not know that those bend ?'- Perhaps they may bend, not being made sufficiently strong.' 'And if they are made sufficiently strong, that will involve an additional expense?'-'It will.' Then if you were to make them of adamant, that would be very expensive?'-'It does not require a very great expense to make them strong enough for heavier work.'

That there might be no deficiency of strength in the fish-bellied rails first laid down upon the Liverpool and Manchester line, they were made of the unusual weight of 35 lbs. to the yard. But the extraordinary speed of the locomotive had not yet been discovered, and there is no doubt that the performances of the 'Rocket' surpassed the expectations of even George Stephenson himself. Although the engine weighed only 4 tons, it proved too heavy-when running at high speeds-for the malleable rails; and as the traffic grew, and heavier engines were introduced on the line, the weight of the rails was increased from time to time, but not in like proportion to the weight of the locomotives. For while the malleable rails have been increased from 28 lbs. to 75 and even 86 lbs. to the yard, the locomotive has been increased from 4 tons, as in the 'Rocket,' to 30 and 35 tons, the weight of first-class express engines. The disproportion between the weight and force of the engine and the resistance of the rail has been constantly increasing; until the point has at length been reached at which no additional weight in the rails will Vol. 120.-No. 239.

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enable them to resist the crushing load of the modern locomotive. As in the case of the battle between guns and iron plates, the weight of both has been increased, until at length, unless a new material-the adamant' imagined by Mr. Alderson-be employed, it is clear that as regards the locomotive and the iron road, the latter will be vanquished in the contest. defect is in the material, to which a crushing power is applied which ordinary iron is positively incapable of resisting. The points of contact of the wheels of a 30 ton locomotive with the rail are very minute, and upon these points the whole weight of the engine presses. The effect is to squeeze and crush the iron and roll it off in laminæ as any one may observe who examines a rail laid down on a line of heavy traffic that has borne a fair amount of work under the heavier class of engine.* On some of the metropolitan lines iron rails, especially if placed on sharp curves, will scarcely last a year. Hence the railroad has become even less permanent' now, with its rail of iron, than it was with its original rail of wood a hundred years ago. It has thus become absolutely necessary to introduce a new material, and that material is to be found in Steel.

The greatly superior resistance which steel offers to crushing as compared with iron, may be learnt from the experiments made by Mr. William Fairbairn, with the object of ascertaining their respective strengths in this respect. A piece of cast iron, both ends flat, was crushed by a pressure to which it was subjected of 55 tons to the square inch; and a piece of malleable iron of the same shape was flattened by a pressure of 73 tons to the square inch; while a piece of steel of the same shape resisted a pressure of 120 tons per square inch without being either crushed or flattened. The result of certain American experiments, quoted by Mr. Mallett, was to a like effect. The mean resistance of cast steel to compression was found to be 295,000 lbs., of cast iron, 125,000 lbs., and of wrought iron, 83,500 lbs. ; while the tensile strength was 40 tons for mild cast steel, 20 to 25 tons for wrought iron, and 10 to 12 tons for cast iron. Thus in cast steel we find a material not only capable of resisting a far greater compressive force than any known metal

*The friction between the driving wheels and the rail, when the engine is thundering along at high speed, is also very great, and the iron is ground off in minute particles, and thrown into the air. Dr. Angus Smith, when once travelling by railway, took the pains to collect some of the particles which floated about him in the carriage and seemed to shine with metallic lustre. On examination they were found to be in reality minute rolled plates of iron, which seemed to have been heavily pressed and torn up from the surface of the rails.

+ Treatise on Iron Shipbuilding.' By Wm. Fairbairn, C.E. 1865. p. 48.

can

can do, but also one whose tensile strength is nearly double that of wrought and more than three times that of cast iron.

The comparatively perishable nature of wrought iron when subjected to the crushing load of the modern express locomotive, has necessarily led to a large increase in the annual cost for maintenance and renewal of railways. Thus, while the percentage of locomotive expenses on gross receipts has somewhat decreased on the Great Northern line during the last fourteen years, the cost of maintenance of way has increased during the same period more than 200 per cent. In an excellent practical paper recently read by Mr. R. Price Williams* before the Institute of Civil Engineers, some striking facts were adduced in illustration of this rapid increase in the tear and wear of permanent way of late years. It was shown that during a period of thirteen years, most of the Great Northern up-line between Potter's Bar and Hornsey, where there are heavy descending gradients, has been renewed not less than three times, giving an average of only 3 years as the 'life of a rail' under heavy coal and passenger traffic worked at high speeds. That it is the pace that kills' as well as the weight, is obvious from another fact stated by Mr. Williams with respect to the Lancashire and Yorkshire line, where an equal number of trains of about the same tonnage as in the case of the Great Northern line, were worked at low speeds over a portion of railway between Bury and Accrington, but there the rails lasted as long as 7 years.

The heavy cost of maintenance and renewals on the London and North-Western Railway has for some time been a marked feature in the accounts of that Company. As the renewal of the road is properly chargeable against revenue, any large increase of expense on this account necessarily tells upon dividend; and hence, to relieve revenue against exceptionally heavy charges for renewals, the expedient of a suspense fund has been adopted by some of the larger companies. But, in 1857, the Suspense Renewal Fund of the London and North-Western Company was found to be so heavily in debt, that the only practical mode that could be devised for dealing with it was to write it off direct to capital to the amount of 256,5881.; and since that date 56,0007. has been charged to capital for renewals in like manner. Great Eastern Company also cut the same knot by charging 86,000l. to capital instead of revenue only two years ago; while the Manchester, Sheffield, and Lincolnshire Company, between the years 1854 and 1861, judging by the accounts, charged

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*On the Maintenance and Renewal of Permanent Way. Read by R. Price Williams, M.I.C.E., before the Institute of Civil Engineers, March 12, 1866.

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renewals direct to capital, without even the pretence of a suspense account. The charge in respect of renewals is always exceedingly variable. During the first few years of working a railway, while the materials are all new, the cost is comparatively light; no provision is made for replacing them when worn out; but as years pass on, and the rails, sleepers, and chairs have to be renewed, the outlay rapidly increases. Thus in 1847, the charge for renewals on the London and North-Western Railway was 381. per mile; in the next five years it was 1017. per mile; and in the ten years following, 2001. per mile; the total expenditure of the Company on renewals of way alone, during nineteen years, having amounted to 1,906,858. The average annual expenditure of the Company for renewals since 1847,' says Mr. Williams, has amounted to 103,0747. This represents something like 73 miles of single way of the main line broken up and entirely replaced annually during the period; chiefly in situations where the traffic was heaviest, and where consequently (owing to the short intervals between trains) the facilities for doing the work are the least, and the danger of accident the greatest.'

The consideration of these circumstances led the officials of the London and North-Western Company to direct their attention to the employment of some more durable material than ordinary wrought iron for rails, with the object of providing a more 'permanent' way than any that had yet been adopted. Mr. Woodhouse, the Superintendent of the Permanent Way Department, induced the Directors, in 1861, to order 500 tons of Bessemer steel rails, which were laid down at such parts of the line as were subject to the most rapid destruction, not only by the passage of the regular traffic, but by the starting, stopping, shunting, and making up of trains. Some of these were laid down in the Crewe Station, and others at Camden Station. Perhaps there is no spot on any railway in Europe where the traffic is so great as at the latter place. At Chalk Farm Bridge there is a narrow throat in the line, at which the whole system of rails employed at the London termini of this great Company converges. There all the passenger, goods, and coal trains have to pass, and the shunting of carriages is constantly going on day and night. The iron rails laid down in this throat were rapidly ground to pieces by the enormous traffic. The face of a rail was usually worn away in little more than two months; and the traffic being so unintermitting, its stoppage for the purpose of changing the rails or renewing them was found most inconvenient as well as dangerous.

Certainly no better spot could have been

fixed upon for determining