The Iron and Steel Manufactures page 3

When, in 1855, Sir Joseph Whitworth turned his attention to the best mode of rifling firearms, it is not surprising that he succeeded in attaining results which surpassed all former achievements. His hexagonal- bored rifle shot farther and more accurately than had ever before been known. His rifled 68-pounder gun was the first to penetrate the four and a half inch iron armour with which the vessels of the royal navy were being plated; and in 1862, in a trial for long range, his nine-inch 310-pounder sent a ball to the unprecedented distance of 11,343 yards, or nearly seven miles.

In regard to the application of wrought-iron to the construction of bridges, buildings, &c., Sir William Fairbairn says that " it was not until some examples had been achieved on a colossal scale that the engineering profession would believe in the possibility of tubular girders and bridges. The investigations and experiments which led to the design and construction of the Britannia and Conway tubular bridges were, however, too convincing to be resisted by the most sceptical. It soon became manifest that an entirely new sphere of action was open to the engineer and the architect." Wrought- iron bridges and girders, though of recent invention, are already amongst the commonest of engineering works; and since the execution of the gigantic works of Stephenson and Fairbairn in wrought-iron, a knowledge of those properties of this metal, which they were the first to utilise, has become one of the most important parts of the education of the civil as well as the mechanical engineer. Of the Britannia bridge it has been said that chains were as unnecessary to support it as intermediate piers (even if the latter could have been built). Its strength is derived from a different source from either. The roof of the bridge consists of two iron platforms, one foot nine inches apart, and fourteen feet broad. The intervening space between the platforms is divided into eight equal parts, by partitions of iron running from end to end of the bridge; and the cells thus formed keep the tube from giving way to compression in the top, where the material is most liable to be injured. Such, in fact, is the cellular or tubular principle of construction which was devised by Sir William Fairbairn, and which was adopted in the construction, not only of the Britannia bridge, but also of the Great Eastern steam-ship, and of numberless other important works. The Great Eastern, the deck of which, built on the principle advocated by Mr. Bourne, is strong enough to balance the bottom, is virtually nothing more or less than a huge hollow iron girder.

"It is now more than thirty years," wrote Sir W. Fairbairn, in 1861, "since it was found desirable to increase the power of steam-engines employed in manufactures; and instead of engines of from 20 to 50 nominal horse-power, as much as 100, and in some cases 200-horse-power, were required to meet the demand. To keep pace with the rapid extension of our manufactures, not only was the power itself doubled, and in some cases quadrupled, but a new class of men was brought into existence as mechanical engineers; and these, with the facilities afforded by new constructions and improvements of tools, gave to the manufacture of machinery of every description an impetus that in a few years - among other things - produced steam-engines in the accelerated ratio of ten to one."

For some years previous to the great demand for enhanced power, mills were driven by single engines, some of as much as 50 or 60-horse-power; but these had soon to give place to others of still greater force, or what was found to answer much better, two were employed coupled together as one engine. Working thus in pairs, they were found to afford greater uniformity of action, from the cranks being placed at right angles. Again, it was found that the speed of 240 feet per minute, considered as the maximum by Watt, was insufficient with the increasing demand for power, and speeds from 350 to 400 feet per minute are now become general. This increase of speed, however, was again soon found inadequate to satisfy the ever-growing requirements for power; and engineers, led by Fairbairn and others, proceeded to utilise still further the expansive force of watery vapour, and to increase the pressure of steam. With the application of steam at increased high-pressure, and an improved principle in the construction of boilers, steam-engines are now made to perform the same amount of work at a cost of only half the amount of fuel that was necessary a few years ago.

'In steam-engines," says Mr. Bourne, in his latest work on this subject, "the tendency is now towards higher piston speeds and higher pressures of steam: and high piston speeds require superior workmanship, especially in the bearings, to prevent heating; and the momentum also of the reciprocating parts should be balanced by counterweights. Unless the bearings of engines are very accurately formed, the oil is forced out of the protuberant or touching parts, and the surfaces heat; whereas, when the rubbing surfaces are very true," the oil is spread over them in a thin film, and metallic contact is prevented. In the engines of the Hercules, which are of 1,200 nominal horse-power, the speed of the piston is 648 feet per minute. In many steam-vessels a pressure of steam of 60 lbs. and upwards is now employed. These engines are fitted with surface condensers; and the steam, after acting by high-pressure in one cylinder, is dismissed into the other, where it acts as low-pressure steam. The consumption of coal is reduced by this arrangement to about 2 lbs. per actual horsepower per hour."

As an instance of the most powerful locomotive engines, the " Iron Duke," used upon the Great Western Railway, may be mentioned. In this engine the cylinders are eighteen inches in diameter, and twenty-four inches stroke. The grate contains twenty-one square feet of area, and there are 305 tubes of two inches diameter in the boiler. The total heating surface is 1,952 square feet, and a cubic foot of water may be evaporated every hour by each five square feet of heating surface. An engine like this, therefore, will exert the power of 750 horses.

In 1868 it was computed by Sir W. Fairbairn that the steam-engines employed in the manufacturing and mining industries of the United Kingdom had an aggregate working capacity of 3,600,000 horse-power; that those employed in steam navigation were equal to 2,420,000 horse-power; and those on railways, consisting of 8,000 locomotives averaging 500 horse-power each, were equal to 4,000,000 horse-power. If this estimate be correct, the total steam-power of the United Kingdom at the date in question was equal to the powers of ten millions and twenty thousand horses. One-fifth of this enormous force was, in the opinion of the same eminent engineer, employed in the manufactures, mills, mines, railways, and shipping of the two counties which are the seat of the cotton industry - the counties of Lancashire and Cheshire - alone.

It would not be easy to enumerate many commodities of greater apparent insignificance than that unpretentious product of the iron industry, the common nail; and yet there are few things of more universal utility. How much is added to the convenience of life by the existence of a cheap and abundant supply of common nails, can only be realised if we would once imagine ourselves without them.

Hutton, in his " History of Birmingham," speaking of the manufacture of these invaluable little articles in the last century, says: " When I first approached Birmingham, in 1741, I was surprised at the prodigious number of blacksmiths' shops upon the road, and could not conceive how the country, though populous, could support so many people of the same occupation. In some of these shops I observed one or more females, stripped of their upper garments, and not overcharged with their lower, wielding the hammer with all the grace of their sex. The beauties of their faces were rather eclipsed by the smut of the anvil. Struck with the novelty, I inquired whether the ladies of this country shoed horses, but was answered, with a smile, 4 They are nailers! ' "

Since that time, when each separate nail had to be made by hand with the help of the most primitive tools, machinery has been introduced whereby the power of production has been incalculably increased. Among the most recent improvements in nail-making machinery may be mentioned an apparatus shown by an English firm at the Paris Exhibition of 1867, which is capable of turning out upwards of half a million nails each working day. The shaft of the machine revolves 120 times per minute, producing eight nails, with head, shank, and point complete, at each revolution, and therefore turning out 960 nails per minute, or 57,600 per hour. Robinson's machine, patented in 1866, instead of operating on a single slip of sheet iron of the width required by the length of the nail, cuts out four rows at once; and one workman is able to manage two of these machines. A new kind of nail, which has been recently introduced from the Continent, and is much used by shoemakers, saddlers, joiners, and others, is made of round wire. The advantage they offer is that they do not cut or split the fibre of the wood so much as square-edged nails, while, at the same time, they are found to hold with greater firmness.

The nails used in shoeing horses are a special class, in which a superior quality of metal and a peculiar shape are requisite. An experienced workman cannot, it is said, as a rule, make more than 1,000 horse-shoe nails a day. It is estimated that of this special kind of nails about one thousand millions are annually produced in England, weighing 5,580 tons, of which about 2,000 tons are exported. An ingenious machine has been patented by Mr. Huggett, by which this class of nails is produced of uniform excellence and quality, and with far greater rapidity than by hand. It was first brought into operation in London. The great centre for the manufacture of nails is still Staffordshire, Worcestershire, and Warwickshire; and now, as in the last century, a very large number of women are employed in the trade. At the census of 1871 there were 10,864 women and 12,367 men returned as nail-makers, making a total of 23,231 persons employed in this manufacture in England and Wales alone.