bilities of construction in its most difficult and expensive form, in case experience should show that such weapons will hereafter be required in our own country. In this connection a comparison with the largest guns produced in England will be of interest. Sir William Armstrong exhibits a 12-ton 9-inch muzzle-loading rifled gun, constructed on the coil principle, and mounted on a wrought-iron carriage and slide; the weight of the projectile is 250 pounds, and the charge of powder 43 pounds. This gun is beautifully made, and is noteworthy from the fact that the compression for checking the recoil is wholly of iron, and is thrown in and out of action by a lever-handle, which is self-acting if neglected. The gun is designed for use on shipboard. The largest Whitworth gun exhibited is a 150-pounder, and is constructed exclusively of mild steel, wrought into tubes, which are forced into each other by hydraulic pressure. But to us the most interesting gun is the 9-inch Paliser gun, made by casting an exterior coating of iron around an interior barrel of wrought iron, constructed on the coil principle. This gun carries a projectile of 250 pounds, and if in practice it should be found to have substantial advantages over our cast-iron guns, it suggests a method by which we may apply the principle to the reconstruction of the large number of cast-iron guns which have been accumulated during the last few years. The gun now manufactured by the British war department, at Woolwich, consists of a cast-steel tube, upon which rings of fibrous wrought iron, made upon the coil principle, are built up, and the specimen exhibited was a 12-inch muzzle-loader, weighing 470 hundred-weight, length of bore 145 inches, having 9 grooves, each 1 inch wide and .2 inch in depth, the spiral increasing from one turn in 1,200 to one turn in 600. The weight of the charge of powder is 70 pounds, and of the projectile 600 pounds.

The only other gun requiring notice was a cast-steel gun, made by Petin, Gaudet & Co., weighing sixteen tons, and intended to throw a projectile of 300 pounds in weight; but it was quite evident that the manufacture of steel and wrought-iron guns in France is still in its infancy, and there would seem to be the same uncertainty in regard to their value as prevails in the United States. But there would seem to be no doubt that within certain limits of size, and perhaps for all sizes of field-pieces, cast steel is regarded as the best material, and Krupp has already produced more than 3,500 cast-steel guns, mostly rifled breechloaders, and at the present time has orders in hand for immediate delivery of 2,200 guns, ranging from 4-pounders to 300-pounders. Not much accurate information is to be procured in regard to the endurance of the larger sized guns, but Krupp exhibited a cast-steel rifled 4-pounder breech-loading gun, belonging to the Prussian war department, which had been fired several hundred times, with gradually increasing charges up to three and three-quarters pounds of powder and 122 pounds of shot, without the slightest appearance of injury.

Although no evidence was afforded by the Exposition of the substitu

tion of cast-steel for cast-iron shot in the French service, my visits to the French iron works seemed to show conclusively that such is the case, as all the large establishments were actively engaged in the manufacture of cast-steel missiles of all sizes, but more especially of the larger calibre; and whatever the fact may be, it is quite evident that cast steel is regarded by French military engineers as superior to all other materials where penetration is required.

Krupp also exhibited a cast-steel rail 50 feet in length, and bent double, cold, in the middle, without fracture. His engineer in the Exposition stated that their annual product of rails was about 30,000 tons, and that no Bessemer steel was employed in their construction. In the absence of a personal visit to the works, we are bound to accept this statement as true, although it is stated on good authority that as many as nine pairs of converters are constantly employed at the works in the production of Bessemer steel, and there seems to be an impression that the tires latterly produced at Essen are not quite equal in quality to the remarkable material which was at first employed for this purpose. This may be only the result of rival representations, and it is undeniable that up to the present time Krupp maintains his pre-eminence in the manufacture of locomotive tires, and is probably justified in the claim which he makes, that his crucible cast-steel coils are superior to those made from Bessemer metal. In the year 1865 the sale of cast-steel tires amounted to 11,396 sets, and the guarantee of their endurance given by Krupp is that they will run 400 kilometres for each kilogram of weight, (equivalent to 125 miles per pound;) that is to say, a tire weighing 600 pounds is guaranteed to run 75,000 miles, but their actual performance as a general rule shows a much higher endurance. The results with these tires and those of other makers-such as Naylor, Vickers & Co., Firth & Sons, the Bochum Company, Petin, Gaudet & Co., the Bowling Company, and the Monk Bridge Company, and other respectable makers, would seem to justify the broad statement that the day for iron locomotive tires has passed by, and that it is far more economical, if not more safe, to substitute cast-steel tires in every case.

The same conclusion cannot yet be affirmed of rails, because the interest account, of but little consequence in the case of the tire, becomes a very serious and indeed controlling element in the case of rails. It may be stated, however, that in all cases where iron rails wear out in consequence of hard service within the limits of duration assigned to a steel tire, it is quite as economical to use steel rails in lieu of iron ones as it is to use steel in lieu of iron tires. But, assuming the cost of caststeel rails to be double that of good iron rails, it is quite evident that there must be a limit in the duration of iron rails beyond which it will not pay to substitute cast steel. This calculation is one which must be made by each consumer for himself, with reference to the available capital at his disposal; but it is safe to declare that on all roads where the iron rail has an average life of ten years it would not be profitable to

substitute cast-steel rails, and so long as the average rate of interest paid by railroad companies in the United States amounts to eight per cent. per annum it would be found expedient considerably to reduce the limit. of ten years above assumed for the duration of iron rails before the substitution of steel rails could be justified on grounds of economy. Even in England, where capital is superabundant and the rate of interest on long obligations not over five per cent., and the traffic per mile of very large dimensions, requiring, as a general rule, the renewal of iron rails in seven years, cast-steel fails have thus far not been very extensively introduced; and even on the London and Northwestern railway, which owns a mill devoted expressly to their manufacture from Bessemer steel, and which, from its enormous traffic, has every inducement to make its road as permanent as possible, the money question seems to check the use of cast-steel rails upon any very extended scale. And yet the necessity of more durable rails than those generally in use is so apparent that any attempt to secure greater durability without much additional cost is regarded with great interest, and hence in the Exposition there were many specimens, and from all the leading nations, of iron rails with steel heads. In some cases the material employed for the head was puddled steel, in others cast steel, and in others Bessemer steel. It seemed to be generally admitted that the durability of the steel in the head was in nowise impaired by its being placed upon a cushion or bed of wrought iron, but the great difficulty appeared to be in securing a thorough union or weld between the two kinds of metal. In the Austrian department, where some admirable specimens of steel-headed rails were exhibited, from the Neuburg Works, the engineer in charge stated that nine per cent. of the heads failed in the weld during the first year, but that subsequently no failures occurred, and that even with this amount of loss the rails were regarded as cheaper than either steel or iron. At Crewe, where the works of the London and Northwestern Company are situated, and where a considerable quantity of Bessemer steel-headed rails have been made, it was stated that some difficulty had been found at first in making a reliable weld of the steel to the wrought iron, and that as many as five per cent. of the rails first made had failed in consequence of the loosening of the steel top; but as experience was acquired in the manufacture this difficulty had disappeared, and the percentage of loss had been reduced materially. The practice at Crewe is to place a bar of soft puddled iron between the steel of the top and the old rails used in the lower part of the rail, and as a further protection the steel for the head is rolled in the form of a channel bar, with ribs in the recessed portion so as to fold around and embrace, as it were, the heal of the rail. Considerable experience has already been acquired in the United States as to the feasibility of making a sufficiently good junction between the iron and steel for a durable rail, and it may be confidently affirmed that there is no practical difficulty in the way of making an iron rail with a steel head, whether of puddled, Bessemer or cast metal, that will meet all the reasonable requirements

of the case, and reduce the failures to less than one per cent. The cost of steel-headed rails is, of course, intermediate between that of all iron and that of all steel rails, and the system possesses the great advantage of rendering all the old rails available for re-manufacture, and of thus renewing the tracks with a bearing surface of steel by gradual steps, and with a very moderate increase of cost. On the London and Northwestern railway, which has had the most experience in the use of Bessemer and steel-headed rails, experience seems to show that the steel-headed rails possess all the requirements in point of cost and durability for their general introduction on the line, and the conclusion is irresistible in my own mind, after a careful study of the specimens in the Exposition, that the steel-headed rail will ultimately prevail over all other kinds of rails now known, and that in the United States the facilities for their manufacture are unusually favorable. It is a question in what manner the steel shall be made for the heads, and this point will be discussed when we come to speak of processes, and it is enough to state here that a good steel head can be made from any one of the kinds of steel above specified.1 In closing this brief statement of the remarkable specimens of cast steel in the Exposition, the products of the Bochum Company (Prussia) should not be overlooked. An enormous cast-steel bell, weighing 29,500 pounds, remarkable for the admirable proportion which existed between its size and its tone, was not, however, more wonderful than the caststeel railway wheels made in sets of ten or a dozen, united by a thin shaft of metal running through the centres, thus enabling one sinking head to answer for the whole quantity, and securing greater density and soundness in the metal. These wheels, when cut apart and turned up, were beautifully sound and clean, and gave evidence of ability to cast steel with as much facility as ordinary cast iron. Another evidence of this was to be found in a locomotive cylinder, bored and of such finish and soundness as not merely to excite general admiration, but induced the belief that possibly it was cast iron which had been deprived of its carbon by being annealed in a bath of oxide of iron, or some other decarbonizing material.

In the Swiss department, machine-cut steel files were exhibited fully equal to any cut by hand; and this result is said to be due to the grinding of the blanks across the face instead of lengthwise, a point which may have great value to our own makers of files.

QUALITY OF MATERIAL.

A careful observer of the iron and steel specimens in the Exposition could not fail to be struck with the varieties in the quality of the metal exhibited and the evident attention paid to the adaptation of special

1 In view of the great interest which this country has in securing good rails, I have obtained permission to insert in an appendix (F) a very valuable paper, recently read before the British Association of Civil Engineers, by C. P. Sandberg, esq., inspector of railway material for the Swedish government.

qualities to special uses. In some establishments only a particular quality would be produced, but, as a general rule, all the large works exhibited, and seemed prepared to produce, a quality proportioned to the price to be paid.

In the pavillion of Le Creusot, for example, seven different qualities · of merchant iron were displayed as examples of the uses to which each quality would be applied, and a personal visit to the works satisfied me that there was nothing fanciful in these grades. In the Welsh iron works it is notorious that the quality of the article produced is directly proportioned to the price paid for it, and in my visits to those gigantic establishments which have grown up in the mountains of South Wales, it was humiliating to find that the vilest trash which could be dignified by the name of iron went universally by the name of the American rail.

This is no fault of the Welsh iron-master, but has arisen from the almost universal practice of late years, on the part of American railroad companies and contractors, of purchasing the lowest-priced article that could be produced. Of course no iron of this quality was to be found in the exposition; but if prizes were to be given for mere human ingenuity, I cannot conceive of anything more entitled to it than the production of a well-finished rail from puddled balls, that will not hold together under the alligator squeezer.

There is, however, one thing more remarkable even than this low quality of iron; and that is, the stupidity and reckless extravagance of the customers who are found to buy it. To this cause, more than any other, is due the necessity of almost annual renewals of rails in the United States, and of the financial troubles of so many of our leading lines of railway; nor is there the slightest excuse for this result, for the Welsh iron-masters, to their credit be it said, make no concealment either of the inferiority of the material, or the poverty of the process by which it is treated, and greatly prefer to turn out work creditable to themselves, and profitable to their customers. But the inexorable law of competition, and the unremitted cry for cheap iron in America, have left them no choice.

For their own country, for the continent of Europe, and for India, no such system is practiced. As a general rule, all rails made for home consumption are guaranteed for from five to seven years, according to the traffic; that is to say, every rail that fails in the slightest degree within the time specified is renewed at the expense of the maker. The extra price paid for a guaranteed rail on roads of moderate traffic is about 30 per cent., but on roads having a heavy traffic at least 50 per cent. additional is paid. In cases where the guarantee cannot be procured in consequence of the heavy usage to which the line, or any portion of it, is subjected, the conclusion is inevitable that a steel rail should be used. And until a similar system of guarantee and adequate pay. ment therefor is introduced into the United States, shareholders in railway companies can place no reliance on the security of their investment and the permanency of dividends.