and groans louder and louder, as his swarthy turban-headed owners keep relentlessly adding package after package to his load. to construct the tubes on the ground than on the aërial platform as first proposed-Mr. Stephenson determined, on mature reflection, to take upon Although it can mathematically be shown that himself the responsibility of reporting to the the two sides of a thin hollow tube are of but directors of the Chester and Holyhead Railway little use except to keep the tops and bottoms at that this extra catenary support, which would their duty-the power of resistance of the latter have cost the company 150,000l., was wholly being, however, enormously increased by the dis- unnecessary. Indeed, such was the superabuntance that separates them-it was nevertheless dance of power at his command, that without necessary to ascertain the precise amount of adding to the weight of the rectangular galleries, lateral strength necessary to prevent the aërial he could materially have strengthened them by gallery writhing from storms of wind. The riv- using at their top and bottom circular flues instead eting process was likewise subjected to severe of square ones, which, merely for the convenience trial, as also the best form and application of the of cleaning, &c., were adopted, although the slender ribs termed "angle-irons," by which not former were found on experiment to bear about only the plates were to be firmly connected, but 18 tons to the square inch before they became the tube itself materially strengthened-in fact, crushed, whereas the latter could only support the angle-irons were to be its bones, the thin plate-from 12 to 14 tons. iron covering being merely its skin. But the security which Mr. Stephenson deemed Mr. Stephenson had two main objects in insti- it necessary to ensure for the public may further tuting the investigations we have detailed. First, be illustrated by the following very extraordinary to determine by actual experiment what amount fact:-It has been mathematically demonstrated of strength could be given to his proposed galler- by Messrs. Hodgkinson and Clark, as well as ies; and, secondly, of that maximum how much practically proved by Mr. Fairbairn-indeed, it will it would be proper for him to exert. And as his be evident to any one who will go through the decisions on these subjects will probably be inter- necessary calculations on the subject that the esting to our readers, most especially to that por-strain which would be inflicted on the iron-work tion of them whose fortunes or fate may doom of the longest of Mr. Stephenson's aërial galleries them occasionally to fly through his baseless by a monster train sufficient to cover it from end fabric, we will endeavor very briefly to explain to end, would amount to six tons per square inch; the calculations on which they appear to have been based. As a common railway train weighs upon an average less than a ton per foot-as the greatest distances between the towers of the Britannia Bridge amount each to 460 feet and as it is a well-known mathematical axiom among builders and engineers that any description of weight spread equally along a beam produces the same strain upon it as would he caused by half the said weight imposed on the centre-it follows that the maximum weight which a monster train of 460 feet (an ordinary train averages about half that length) could at one time inflict on any portion of the unsupported tube would amount to 460 tons over the whole surface, or to 230 tons at the centre. which is exactly equal to the constant stress upon the chains of Telford's magnificent suspension Menai Bridge when, basking in sunshine or veiled in utter darkness, it has nothing to support but its own apparently slender weight! Lateral strength.-The aërial galleries having, as above described, been planned strong enough for the safe conveyance of goods and passengers at railway speed, it became necessary to calculate what lateral strength they would require to enable them to withstand the storms, tempests, squalls, and sudden gusts of wind to which from their lofty position they must inevitably be exposed. to The utmost pressure of the hurricane, as estimated by Smeaton-but which is practically considered to be much exaggerated-amounts about 46 lbs. to the square foot; and this, on one of the larger tubes (460 feet long by an average of rather less than 30 feet high) would give a lateral pressure of 277 tons over the whole surface, or of 133 tons on the centre. Now, to ensure security to the public, Mr. Stephenson, after much deliberation, determined that the size and adjustment of the iron to be used should, according to the experiments made and recorded, be such as to enable the aforesaid un- To determine the competency of the model supported portions of the tube (each 460 feet in tube to resist proportionate pressure to this length) to bear no less than 4000 tons over its amount, it was turned over on its side; and, whole surface, or 2000 tons in the centre, being having by repeated experiments been loaded and nine times greater than the amount of strength overloaded until it was crushed, the result fully necessarily required; and as the results-unex- demonstrated to Mr. Stephenson's satisfaction its pected as well as expected-of the searching power to resist, according to his desire, a lateral investigation which had been instituted, incontesta- pressure more than five times greater than that bly proved that this Herculean strength could be which it is in the power of the hurricane to imparted to the galleries without the aid of the inflict. chains, which, even as an auxiliary, had been The experimental information required by Mr. declared unnecessary-and as Mr. E. Clark had Stephenson having, by the zeal and ability of Mr. very cleverly ascertained that it would be cheaper | Fairbairn, Mr. Hodgkinson, and Mr. Clark, been finally obtained, the next points for consideration they walked every morning and evening, in addicame to be, where these gigantic twin-tubular tion to their daily work; the remainder gypsying galleries should be constructed, and, when con- in the encampment in various ways, of which the structed, by what power, earthly or unearthly-it following is a sample: will appear that the latter was found necessary— 64 An Irish laborer, known only by the name of they should be raised to the lofty position they " Jeminy," bought for himself a small clinkerwere decreed to occupy. built room. As "lodgings," however, soon rose After much reflection on Mr. Clark's valuable in price, and as he had not time to keep a pig, he suggestions on these subjects, Mr. Stephenson resolved to be satisfied henceforward with half his determined-1st. That the four shortest galler- tiny den, and accordingly let the remainder to a ies, each 230 feet in length, (to be suspended at much stronger fellow-countryman, who, being still the height in some places of 100 feet between the less particular, instantly let half of his half to a two land towers and the abutments of the ap- very broad-shouldered relation, until, like other proaching embankments,) should, as he had orig-Irish landlords we could name, poor “Jemmy" inally proposed, be at once permanently con- found it not only very difficult to collect, but danstructed on scaffoldings in the positions in which gerous even modestly to ask for, "his rint!" and they were respectively to remain; 2ndly. That thus in a short time, in consequence of similar the four longest galleries, (each 472 feet in length,) pressure from without," almost every chamber which were eventually to overhang the Straits, was made to contain four beds, in each of which should be completely constructed at high-water | slept two laborers. mark on the Carnarvon shore, upon wooden platforms about 400 feet westward of the towers on which they were eventually to be placed; 3rdly. That to the bases of these towers they should, when finished, be floated on pontoons, from which they were to be deposited on abutments in the masonry purposely made to receive them; and 4thly. That the tubes should be raised to and finally deposited in their exalted stations by the slow but irresistible power of hydraulic presses of extraordinary force and size. As soon as the preliminary wharves, platforms, shanties, and workshops were completed, there instantly commenced a busy scene, strangely contrasted with the silence, tranquillity, and peaceful solitude that had previously characterized the spot. While large gangs of masons were excavating the rocky foundations of the land towers, sometimes working in dense groups, and sometimes, in "double quick time," radiating from each other, or rather from a small piece of lighted slow-match, sparkling in the jumper-hole of the rock they had been surrounding; while carts, horses, and laborers in great numbers were as busily employed in aggregating the great embankments by which these towers were to be approached; while shiploads of iron from Liverpool-of Anglesey marIn the rear of this immense wooden stage, ble from Penmon-of red sandstone from Runcorn which extended along the shore no less than half in Cheshire-at rates dependent upon winds and a mile, covering about three acres and a half, tides, were from both entrances to the Straits apthere were erected three large work-shops, con- proaching or endeavoring to approach the new taining forges and machinery of various descrip- wharves; while almost a forest of scaffold balks tions, for belaboring, punching, and cutting plate- of the largest and longest description-like Biriron. There were likewise constructed five nam wood coming to Dunsinane-were silently wharves with cranes for landing materials, as also gliding towards the spot; while wagons, carts, six steam engines for constant work. II. CONSTRUCTION OF THE TUBES AND TOWERS. -The locality selected for the formation of the tubes having been cleared, a substantial platform, composed of balks of timber covered with planks, was very quickly laid down. ber of men to be employed was On iron-work about. At stone-work for the towers Total. The num-post-chaises, gigs, horses, ponies, and pedestrians, 700 800 1,500 some of the latter carrying carpet-bags and some bundles, &c., were to be seen on both sides of the Straits eagerly converging across the country to the new settlement, or diverging from it;-the unremitting clauk of hammers—the moaning hum of busy machinery-the sudden explosion of gunTemporary shanties or wooden cottages, white-powder-the white vapor from the steam-engines washed on the outside, like mushrooms suddenly—and the dark smoke slowly meandering upwards appeared in the green fields and woods immedi- from their chimneys, gave altogether interest, ately adjoining; besides which, accommodation animation, and coloring to the picture. was provided for a schoolroom, schoolmaster, As our readers will, however, probably be clergyman, and, in case of accidents, a medical anxious to know how the great tubes which have man; the whole being agreeably mixed up with a been delineated are practically constructed, we proportion of wives, sweethearts, and children, will shortly describe the operation, which, we are sufficient for cooking, washing, sewing, squall- happy to say, is contained in a vocabulary of only ing, &c. Nevertheless, notwithstanding these three words, these aerial galleries being solely alluring domestic arrangements, many sturdy, composed of-Plates-Rivets-and Angle-Irons. independent workmen preferred sleeping in vil- Plates. The wrought iron plates which form lages four and five miles off, to and from which the top, bottom, and sides of the Britannia "land tubes," 230 feet in length, are, of course, slighter | she is kneading, or as the child Horner perforated than those required for the four, each 460 feet, the crust of his Christmas pie, when which overhang the stream. For these long tubes-which are of the same height and breadth as the shorter ones—the dimensions of the plates are as follows : For the bottom. He put in his thumb And said-What a good boy am I! Some of the steam arms or levers just described are gifted with what may be termed 12 feet in length, 2 feet 4 inches to 2 feet 8 inches" double-thumbs," and accordingly these perforate in breadth, to inch in thickness. For the top. 6 feet in length, 1 foot 9 inches to 2 feet 1 inch in breadth, to inch in thickness. For the sides. two holes at a time, or forty per minute-the When the plates, averaging from six to twelve feet in length by above two eet in breadth, have feet to 6 feet 6 inches in length, 2 feet in been thus punched all round, and before they are breadth, to inch in thickness. brought to the tube, they are framed together on the ground in compartments of about twenty plates each, (five in length and four in breadth,) in order to be connected to each other by what are termed covering-plates and angle-irons. Although these plates have been severally forged with every possible attention, yet, to render them perfect in thickness, they are not allowed by Mr. Stephenson to be used for the tubes until each In order to prepare the former (which are half has been passed by the company's superintendent an inch in thickness, one foot in breadth, and between two uncompromising massive iron rollers, about two feet long) they are heated in a small worked by steam, which, by revolving, quietly furnace, when, instead of passing between rollremove or rather squeeze down that variety of eis, they are put under a stamping, or, as it is pimples, boils, lumps, bumps, and humps, which, technically termed, a joggling block, which by from unequal contraction in the process of cooling,|repeated blows renders their surface perfectly flat; occasionally disfigure the surface of plate iron, after which a series of holes, corresponding in size and which in the workman's dictionary bear the as well as in distance from each other with those generic name of "buckles." When the plates, in the "plates," are punched all along the outer the largest of which weigh about 7 cwt., have edge of each of their four sides. When thus prebeen thus accurately flattened, they are one after pared, two of these small covering plates-one another, according to their dimensions, carried by on each side—are made to cover and overlap the two or more men towards one of several immense horizontal line of windage existing between the cast iron levers, which, under the influence of edges of the plates, which, as we have stated, steam, but apparently of their own accord, are to have been previously arranged so as to touch each be seen from morning till night, whether sur-other; and bolts being driven through the correrounded by workmen or not, very slowly and very indolently ascending and descending once in every three seconds. Beneath the short end of this powerful lever there is affixed to the bottom of a huge mass of solid iron a steel bolt-about the length, thickness, and latent power of Lord John Russell's thumb-which, endowed with the enormous pressure of from 60 to 80 tons, sinks, at every pulsation of the engine, into a hole rather larger than itself, perforated in a small anvil beneath. sponding holes of the three plates, (the large plates lying between the two covering ones,) they are firmly riveted together by the process we shall now describe. Rivets. In the construction of the Britannia tubes there have been required no less than two millions of bolts, averaging ths of an inch in diameter and 4 inches in length. The quantity of rod-iron consumed for this purpose has therefore amounted in length to 126 miles, and in weight to about 900 tons! The mode in which these legions of rivets have been constructed is briefly as follows: At the western end of the company's principal forging establishment there stands a furnace or As soon as the laborers of the department bearing each plate arrive at this powerful machine, the engineer in charge of it, assisted by the carryingmen, dexterously places the edge of the iron upon the anvil in such a position that the little punch|trough, full of pieces of rod-iron from 3 to 47 in its descent shall consecutively impinge upon inches in length, packed together as closely as one of the series of chalk dots, which, at four soldiers in a solid square of infantry. As soon inches from each other and 14 inch from the edge, as by the fiery breath of bellows worked by steam, have been previously marked around the four they have been made uniformly red-hot, a little sides of the plate; and thus four rows of rivet-boy, whom they are all obliged to obey, rapidly, holes averaging an inch in diameter are, by the and without partiality, favor, or affection, picks irresistible power we have described, pierced them out one after another through the furnacethrough plate-iron from one half to three fourths door with a pair of pincers, from which he quietly of an inch in thickness, quite as easily as a young drops them perpendicularly into eight moulds, cook playfully pokes her finger through the dough each of which being about of an inch shallower than the length of the piece of iron it respectively head until his comrade, by repeated blows of his receives, they of course all equally protrude about that distance above the surface. In this position they are handed over to a pale, sturdy engine-man, or executioner, who, with about as much mercy as Procrustes used to evince towards those who slept on his bed, immediately places them upon an anvil, towards which there very slowly descends a huge superincumbent mass of iron pressed downwards by an immense long cast iron lever worked by steam. By this despotic power, the red protruding portion of each little rod is by a single crunch inexorably flattened, or "fraternized;" and thus suddenly converted-nolens volens-into a bolt, it is no sooner thrown upon the ground, than the mould from which it was ejected is again, by the child in waiting, filled with another raw red-hot recruit, who, by a process exactly the reverse of decapitation, is shortened, not by the loss but by the acquisition of a head! However, after all, just as “the Marquis ofis not the Duke of -," so is a bolt not a rivet, nor does it become one, until, like a bar-shot, it is made double-headed, an important process which has now to be described. As soon as each "set" of the half-inch iron plates which form the sides, top, and bottom of the Britannia tubes, have by a travelling crane been lifted-technically termed "picked up"-into their places, and have been made to touch each other as closely as possible, a movable stage on wheels is drawn close to the outside of the tube, for the purpose of firmly connecting every set of plates to that which on each side adjoins it. This work is performed by what is termed " a set of riveters," composed of two "riveters," one 66 holder-up," and two rivet-boys. hammer, has swaged it into a workmanlike form. The bolt is thus finally converted into a rivet, which, by contracting as it cools, binds together the plates even more firmly than they had already been almost cemented by the irresistible coercion of three sledge-hammers; indeed, they are so powerfully drawn together, that it has been estimated it would require a force of from four to six tons to each rivet to cause the plates to slide over each other. The bolts for the upper holes of the interior, which, being about 30 feet high, are of course completely out of the rivet-boy's reach, are dropped by him into a concentric iron ring, which, by a wire and cord passing over a pulley attached to one of the uppermost plates, is rapidly raised, until the holder-up is enabled by pincers to grasp the fiery iron, which, on being inserted into its hole, he then instantly, as before, presses with his hammer. By the operations above described, "a set of riveters" usually drive per day about 230 rivets, of which in each plate there are about 18 per yard, in two rows, averaging only 2 inches of clear space between each bolt-head. On the large tubes alone there have been employed at once as many as 40 sets of riveters, besides 26" platers," or men to adjust the plates, each having from three to four men to assist him; and when this well-regulated system is in full operation it forms altogether not only an extraordinary but an astounding scene. Along the outside of the tube, suspended at different heights, are to be seen in various attitudes 80 riveters-some evidently watching for the protruding red bolt, others either horizontally swinging their sledge-hammers, or holding the rivet swage. As soon as the two first have ascended the scafIn the inside of this iron gallery, which is in folding on the outside of the tube, and when the comparative darkness, the round rivet-holes in the holder-up, sitting on a board suspended by ropes sides as well as in the roofs, not only appear like from the roof, has exactly opposite to them taken innumerable stars shining in the firmament of up his position on the inside, one of the boys quickly heaven, but the light beaming through each forms abstracts from a travelling furnace, conveniently another as bright a spot either on the ground or on placed for the purpose, a red-hot bolt, which by a the internal surface of the tube. Amidst these circular swing of his pincers he hurls inside the constellations are to be faintly traced, like the figtube towards the other boy, his comrade or play-ures on a celestial globe, the outlines of the holdfellow, who, as actively as possible, with a similar ers-up, sitting at different altitudes on their respecinstrument snapping it up, not only runs with it towards the holder-up, but as long as he can reach the rivet-holes inserts it for him therein. As soon as this is effected, the holder-up presses against it an enormous iron-hammer, which forces it outwards until it is stopped by its own head. The red protruding bolt is now mercilessly assailed by the two riveters, whose sledge-hammers meeting with a sturdy reaction from that of the holder-up, which by a vast leverage or length of handle elastically returns blow for blow, the bolt, in about thirty seconds, becomes double-headed, when one of the riveters, dropping his hammer, snatches up a steel mould about 9 inches long, called a swage, which he continues to hold upon the newly-formed tive stages. Beneath them 40 or 50 rivet-boys are dimly seen, some horizontally hurling red-hot bolts, others with extended pincers running forwards with them, while fiery bolts, apparently of their own accord, are to be observed vertically ascending to their doom. This cyclopean dance, which is of course most appropriately set to music by the deafening reverberations of 70 or 80 sledgehammers, is not altogether without danger, for not only does a “holder-UP” from a wrong movement occasionally-like a political Phaeton-all of a sudden tumble down, but the rivet-boys, generally unintentionally, but occasionally, it is said, from pure mischief, burn each other more or less severely, in which cases a couple of these little sucking Vulcans, utterly unable, from incessant | whom they may burn, they very dexterously, by a noise, to quarrel by words, fall to blows, and have sudden swing of their pincers, throw them almost even been observed to fight a sort of infernal duel perpendicularly about 45 feet, or about 10 feet with pincers, each trying to burn his opponent higher than the top of the tube, upon which, as we anywhere and everywhere with his red-hot bolt! have stated, they fall among the assembled rivetBut by far the most curious part of the riveting ers as if they had been dropped from the moon. process is to be seen on the flat roof or top of the As soon as these red-hot meteors descend upon tube. This immense deck, which we have already the flat roof, another set of rivet-boys eagerly snap stated to be 472 feet in length, is composed of a them up, and each running with his bolt, not to pavement of plates to be connected together by 18 the spot where it is required, but to one of certain longitudinal rows of rivets, the heads of which are holes in the plate made on purpose for its inserto be only 2 inches apart. Beneath this surface, tion, he delivers it into the pincers of the little at a depth of only 1 foot 9 inches, there is, to give sweep, rivet-boy, or Ascanius within the flue, who, additional strength, a similar stratum of plates, the having been patiently waiting there to receive it, space included between both being divided into crawls along with it towards his Pius Æneas, the eight compartments called flues, 21 inches deep by stout recumbent holder-up. As soon as he reaches 20 inches broad, exactly resembling those of a com- him he inserts for him the small end of the bolt mon stove. After the horizontal bottoms and up- into the hole for which it has been prepared, and right sides of these eight flues have been firmly through which, in obedience to its fate, it is no connected together by the battering process we sooner seen to protrude, than the sledge-hammers have just described, the upper stratum of plates of the expectant riveters, severely jerking at every is loosely laid down, and, being thus by the super-blow the heavy leg of the poor holder-up, belabor incumbent weight of the iron covering securely it and "swage" it into a rivet. adjusted, their final connection is effected as follows: A tiny rivet-boy-we observed one little mite only ten years of age-in clothes professionally worn into holes at the knees and elbows-crawling heels foremost for a considerable distance into one of these flues as easily as a yellow ferret trots into a rabbit-hole, is slowly followed by his huge lord and master, the holder-up, who exactly fits the flue, for the plain and excellent reason, that by Mr. Stephenson the flue was purposely predestined to be exactly big enough to fit him; and as, buried alive in this receptacle, he can move but very slowly, he requires some time, advancing head foremost, to reach the point at which he is to commence his work. On arriving there, his first process, lying on his left side, is with his right hand to pass through one of the rivet-holes in the plate above him a little strong hook, to which is attached a short hempen loop, or noose, which, supporting the heavy end of his huge hammer, forms a fulcrum upon which he can easily raise it against the roof, simply by throwing his right thigh and leg over the extremity of the long lever or handle of the instrument. When similar preparations, by the injection of other little rivet-boys and other stout holders-up into several of the other flues, have been made, the signal for commencing operations is given by several red-hot bolts falling, apparently from the clouds, among the riveters, who, leaning on their sledge hammers, have been indolently awaiting their arrival. These bolts have been heated on the outside of the tube on the ground immediately beneath, in a portable furnace, from which a gang of lithesome rivet-boys in attendance extract them as fast as they are required, and then walking away with them, without looking upwards, or apparently caring the hundred-thousandth part of the shaving of a farthing where they may fall, or The red-hot iron-unlike the riveters-cools during the operation we have just described; and even if a by-stander, from being stone-blind, could not see the change in its temperature, it could easily be recognized by the difference in the sound of the hammers between striking the bolt while it is soft and hot, and when it has gradually become cool and hard. But whatever may be the variety of colors or of noises which accompany the forma tion of every one of these roof-rivets, it is impossible to witness the operation we have just described without acknowledging, with a deep sigh, how true is the proverb that "one half of the world," especially the rich half, "does not know how the other half lives;" indeed, unless we had witnessed the operation, we could scarcely have believed that any set of human beings, or rather of fellow-creatures, could professionally work from morning till night, stuffed horizontally into a flue of such small dimensions-that they could endure the confinement which only allows them, by changing from one side to another, to throw sometimes the right leg and sometimes the left over the elastic handle of a hammer-and above all that they could bear the deafening noises created close to and immediately thundering into their very ears! In attentively watching the operations just described, we observed that at the sides of the tube it required generally eighteen blows of the hammer to flatten the end of the bolt, and then twelve blows on the "swage" to finish the head of the rivet; whereas, on the roof, the former operation was usually effected by only twelve blows, and the latter by eight or nine. At first, we conceived that this difference might be caused by a reduction in the sizes of the plates and bolts; but those in the roof proving to be the thickest and longest, we, on a few moments' reflection, ascertained that the reduction of labor in riveting the roof is caused by the sledge-hammers descending upon it by grav |