made in so enormous a surface must of course be very great, and it became therefore expedient to devise some means of punching them, which would at once insure regularity of position and expedition in execution. Messrs. Roberts succeeded in perfecting a most powerful punchingmachine, which performed its work with incomparable accuracy and despatch. By its means the enormous number of plates composing this structure were perforated with a precision and speed, themselves an engineering marvel. The ceiling of the tube is composed of eight cellular tubes, each of which is about 20 inches in width, and 21 high; these cells are likewise formed of wrought-iron plates, which are three-quarters of an inch thick in the middle, and half an inch towards the ends of the tube. The joints of these plates are strengthened like the others. The floor of the tube contains six cellular tubes, about 27 inches in width, and 21 high, formed as above, with the addition of a covering plate of iron over every joint on the under-side of the tube. The sides are united to the ceiling and floor by double angle irons within and without. The entire length of this great tunnel of iron is 412 feet: it is 14 feet in extreme width; it is also a little higher in the middle than at each end, being 22 feet 3 inches high at the ends, and 25 feet in the middle; this, however, includes the diameter of the cells top and bottom. Each end of the tube, where it rests upon the masonry, is strengthened by cast-iron frames to the extent of about 8 feet of the floor. The entire weight of this stupendous piece of iron-work is about 1300 tons! The sensitiveness of such a mass of metal to alterations in atmospheric temperature must be very great, and unless especially provided against, would, slight as the cause may appear, soon produce the most destructive effects upon the solidity of the whole structure. Some who read this account may not be able to form a proper estimate of the power exerted by metal expanding or contracting under changes, of temperature; but in illustration, it may be mentioned that hot-water pipes incautiously placed so as to abut against a wall at each end, have on more than one occasion almost pushed the wall down, so soon as the circulation of hot water was established in them. The expansions and contractions of so long and large a metallic mass must necessarily be very considerable, and they were provided for by a very ingenious and simple contrivance. The ends of the tube rest upon twenty-four pair of iron rollers, connected together by a wrought-iron frame. The tube is also partly suspended to six cast-iron beams, underneath the extremities of which are twelve gun-metal balls six inches in diameter. These contrivances act like castors to the ponderous machine, and facilitate its contractions or expansions as they severally may occur. We have a fancy that this great tube might be made to serve the purpose of a huge thermometer, by attaching some simple leverage and dial-plates to its extremities; and we are sure that important practical results might be attained by the adoption of our suggestion as to the expansibility of large masses of iron exposed to the vicissitudes of our climate-results, the grand scale of which would render them available for all similar undertakings in future. The iron colossus is in its place; but by what gigantic upheaving power is it to be lifted 20 or 24 feet high into the air, and held there until its permanent bed is all ready to receive it? The mass to be lifted is upwards of 400 feet long, and weighs about 1300 tons! Can it be done? is the very natural question which presents itself to the mind. At each end of the tube is the iron answer-in a couple of steam-engines and two hydraulic rams. It appears that the task of elevating this vast fabric was intrusted by Mr. Stephenson to the talented hydraulic engineers Messrs. Easton and Amos. At each pier, resting upon massive bearing-girders of cast-iron, solidly imbedded in the masonry, was placed a large hydraulic ram. This machine consisted of a cylinder 3 feet in diameter to the outside, with a cylindrical cavity of about a foot and a half in diameter, so that the actual thickness of this powerful cylinder was nine inches of solid iron all round! In it was the ram,' a cylindrical mass of solid iron 18 inches or so in diameter, so that it did not fit the cylinder quite accurately, but left a vacuity for the passage of water to the bottom. Attached to the top of this ram is a transverse piece of metal called a 'crosshead,' 2 square feet thick, with two square apertures, through which the great chains which are to lift the mass are passed and secured. The chains consisted of flat bars of wrought-iron about 6 feet in length, 14 inch thick, and 7 inches wide. Each ram lifted two chains composed of nine links, containing eight bars in the upper links, but four only in the lower. The stroke of the ram was 6 feet-that is, it lifted the tube 6 feet in its full range. In the recess where the fellow-tube is to be placed, a steam-engine of peculiar construction was erected, to whose obedient toilings the mighty work of raising the tube at each end was committed. These steamengines were on the high-pressure principle, the cylinder being placed horizontally, and the piston-rod running completely through the cylinder at both ends, where it was connected with fly-wheels and the plungers of the force-pumps. The length of the stroke was 16 inches. At the summit of the cylinder of the hydraulic press was a small tube, the internal cavity of which was only three-eighths of an inch in diameter. This tube was connected with the force-pumps. Regarded in itself, this little tube was the least imposing portion of the whole mechanism; and no one who looked at it by the side of the vastlyproportioned instrument it was attached to, would have believed that that tiny cylinder was the channel of a force equalling 700 or 800 tons! Could it be possible that this vast work was to be lifted by the direct instrumentality of two tubes with a bore the size of a quill barrel ?* Such are the wonderful results which the laws of hydraulic science have placed within our reach, bringing to our aid a power of such vast proportions as it never entered Eastern imagination to endow a geni or an afrit with. All things being now ready, the lift-chains firmly secured to both ends of the tube, the steam up, and the workmen at their posts, the great operation commenced. The steam-engines acting simultaneously, and with equal velocity and power at each pier, the mighty structure began to rise. This was indeed an anxious moment, as the whole iron structure hung suspended by the hydraulic engines at each end. The engines worked with a will, as the saying is; and amid the buzz of voices, the rapid puff-puffs of the escape-pipe, the muffled sound of clacking valves, and the hurrying to and fro of swarthy mechanics, the Tube Bridge rose majestically, but with great slowness, into the air. At every rise of 6 feet the engines were stopped, and the chains readjusted to the head of the ram, and the top links removed. By a succession of such rises, the tube finally reached the desired elevation of about 24 feet, and there dangled in the air, as though a mere plaything in the hands of the two hydraulic giants. It was then allowed to take its permanent position on the massive masonry prepared for it; the anxiety of its erection was at an end; and the Tube Bridge lay across the river, a monument of the combined skill of British engineers of the nineteenth century. Its sustaining power still remained to be tested. Carriages, heavily laden to the amount of many hundred tons, were placed in its centre, and allowed to remain there for two or three days; but the deflection did not, we believe, exceed an inch and a half, and disappeared on the removal of the weight, thus demonstrating its resistance and its elasticity. Since then, it has been con • To give our readers a conception of this part of the process, it may be noted as an established principle in hydraulics, that a closed vessel being filled with water, and by means of a tubular opening a pressure exerted on a part of the surface, an equal pressure is propagated through the fluid to every part of the same surface. Hence,.if in the case before us, the water was forced through a tube three-eighths of an inch in diameter into a cylinder with a movable piston eighteen inches in diameter, the force exerted upon the latter would bear the same ratio to that which acted upon the former, as the square of eighteen bears to the square of threeeighths; the areas of circles being as the squares of their diameters; that is, the force would be multiplied 2304 times. Thus we may perceive that this tube bridge 412 feet in length, and weighing 1300 tons, was raised through a height of 24 feet, by forcing water with machinery, impelled by steam, into tubes threeeighths of an inch in diameter; and that the force applied to the elevation of the bridge, was about two thousand times as great as that directly exerted by the engines.-[ED. stantly worked; and the vast hollow, which a few months ago resounded with the deafening clatter of the riveters' hammers, now roars with the rush of carriages, and re-echoes in a voice like thunder the hoarse and impetuous expirations of the flying locomotive. The mathematicians still nurse their forebodings; but may it never be that a work of so much skill and ingenuity, and the destruction of which would inevitably involve so fearful a loss af life, should become a mass of ruins! We do not share these fears; experiment has long since settled the question; and we believe that nothing but some anomalous and unforeseen class of circumstances could injure the security of the Tube Bridge. The Tube Bridge is pre-eminently a work of our own era: it is one of those vast and complicated efforts of skill which no previous period of the world's history could command. Whether we consider the inass of metal employed for these structures in the positions above stated, or the cost of the undertaking, or the difficulties of its construction, elevation, and location, or the novelty of the principle, we are presented with a theme of admiration and astonishment which posterity will not exhaust. ECONOMY. I have a few words to say to mothers on a point of domestic economy. In a country like ours, where there are few large estates, and where almost every father of a family is subjected to some kind of labour, either for the maintenance of those who are dear, or the preservation of possessions on which they are to depend when he shall be taken from them, the duty of the "help-meet," to lighten as far as possible the burdens by a consistent economy, is too obvious to need illustration. To adapt whatever may be entrusted to her care, to the best ends, and to make it subservient to the greatest amount of good, should be her daily study. There is, perhaps, no community of women, who more faithfully, or dexterously, than the wives and mothers of New England, carry this wisdom and forethought into all the details of that science by which the table is spread, and the apparel adapted to the ever-changing seasons. The same judgment which so admirably regulates food and clothing, it would be desirable to apply to an other and a higher department. It is to mothers with the care of young children, that these re marks on economy are peculiarly addressed. They have the charge of immortal beings, whose physical, mental and moral temperament, are for a long period, exclusively in their hands. Nothing save the finger of God has written on the tablet, when it is committed to them. It is important that they secure time to form deep and lasting impressions. Let them, therefore, devote their first strength, and their utmost effort, to the highest duties. became spiritless, nervous and discouraged. She was harassed by the application of force among the inferior machinery. When it was necessary that power should be brought to bear upon the minds committed to her care, she was painfully conscious that her energies had spent themselves in other channels. Running up the shrouds like a ship-boy, the helm where she should stand, was left unguided. The pilot, steering among rocks, does not weary himself with the ropes and rigging, which a common sailor as well manages, and better understands. The heart soon developes itself, and asks cul- | family, mental diseases were disclosed. She ture. Through the feelings and affections it bursts forth, even while the infant is considered not to have advanced beyond animal nature. The preferences, the passions, reveal themselves, like the young tendrils of the vine, reaching out feebly and blindly. The Mother must be assiduous, in teaching them where to twine. While the character of the babe is forming, let every action and indication of motive, be a subject of observation. But how can she be adequate to this, if the whole attention to the personal comfort of several young children devolves upon herself? If she is to make and mend their articles of dress, bear them in her arms during their period of helplessness, and exhaust herself by toils throughout the day, and watchings by night, how can she have leisure to study their varying shades of disposition, and adapt to each the fitting mode of discipline, as the skilful gardener suits the plant to the soil? Will she not be sometimes moved to apostrophize them, like the leader of the wandering, repining Israelites, "how can I alone bear your encumbrance, and your burden, and your strife?" The remedy is, for the mother to provide herself with competent assistance, in the sphere of manual labour, that she may be enabled to become the constant directress of her children, and have leisure to be happy in their companionship. This would seem to be a rational economy. "My husband cannot afford to hire a nurse for the little ones," said a young friend. "We have so many, that we must economize." Her mother suggested that the expenditure should be saved in some other department of housekeeping, in the toilette, or in luxurious entertainment. But the counsel was not accepted by the danghter, who in her zeal for economy, failed to comprehend its elementary principles. She commenced her task with vigour and confidence in the correctness of her own decision. Sickness in the various forms that mark the progress of dentition, and neglect of slight diseases in their first symptoms, came upon her young family. Uninstructed by experience, she gave powerful medicines for trifling maladies, or summoned and teazed physicians, when Nature was simply perfecting her own operations. The children who had emerged from infancy, were indulging bad dispositions, and acquiring improper habits. She knew it. But what could she do? She was depressed by fatigue. The wardrobe of her numerous little ones, continually required her attention. It would not do for them to be unfashionably clad, or appear worse than their neighbours. So, the soul being most out of sight, must suffer most. Blindness to evil, or hasty punishment, rendering it still more inveterate, were the only sources of her hurried and hurrying mode of existence. For her, there seemed no rest. If health returned to her young The temper and constitution of the young mother became equally impaired. Her husband complained of the bad conduct and rude manners of the children. "What could she do? She was sure there was nothing but toil and trouble, by night, and hy day." This was true. There was an error in economy. The means were not adapted to their highest ends. Is this an uncommon example? Have we not often witnessed it? Have we not ourselves exhibited some of its lineaments? The proposed remedy, is to employ an ef ficient person, in the nurse's department. I say efficient, for the young girls, to whom this responsibility is sometimes entrusted, are themselves an additional care. "I am not willing," said a judicious father, "to place my infant in the arms of one, with whom I would not trust an expensive glass dish." The physical welfare of infancy is of such immense importance, that it seems desirable that those whom the mother associates with herself in this department, should have attained full strength, both of mind and body. Moral integrity, patient and kind dispositions, industrious habits, and religious principles, are essential to the faithful discharge of these deputed duties, and to render that influence safe, which they will necessarily acquire over the little being whose comfort they promote. Such qualities are deserving of respect, in whatever station they may be found, and I would suggest both as a point of policy and justice, the attaching higher consideration to the office of a nurse, when her character comprises them. If the nurture of an immortal being for immortality is an honourable work, and if its earliest impressions are allowed to be most indelible, those who minister to its humblest wants, partake in some measure of its elevated destiny; as the porters and Levites derived dignity from the temple-service, though they might not wear the Urim and Thummim of the HighPriest, or direct the solemn sacrifices, when the the flame of Heaven descended upon the altar. To the inquiry why this kind of assistance is more needed by the mother in our own days, than by her of the "olden time," by whom the care of children, the operations of the needle, the mysteries of culinary science, and all the complicated duties of housekeeping, were simultane ously performed, without failure or chasm, the natural reply is, that the structure of society is different; and from an educated parent, the modern system of division of labour, asks new and extended effort. She requires aid, not that she may indulge in indolence, but that she may devote the instruments entrusted to her, to their legitimate uses. There is, perhaps, no sphere of action, where indolence is both so fatal and so sinful, as in that of a mother of young children. She is a sentinel who should never sleep at her post. She cannot be long relieved without hazard, or exchanged without loss. She should therefore be careful of her strength, her health, and her life, for her children's sake. If she employ a subaltern, it is that she may give herself more exclusively to their highest and best in terests. Let her be persuaded, whatever may be the demands upon her time, or their advantages for gaining knowledge from other sources, to spend systematically a portion of time in their daily instruction. Let her also be with them, when they retire at night, to review the day's little gatherings and doings, and to point the tender spirit to the Giver of all its gifts. Let the period devoted to them, be as far as possible uninterrupted by the presence of others, and chosen, in the morning, before care has seized the teacher's mind, or temptation saddened the beloved pupil. Let the time be spent in reading some book adapted to their comprehension, conveying useful knowledge or moral and religious instruction, questioning them respecting its contents, adding such illustrations as the subject or their peculiar state of intellect and feeling may render appropriate; having it always understood that at night some recapitulation will be expected of the lessons of the day. The Mother who regularly does this, will find herself in the practice of a true and palpable economy. She will be induced to furnish herself with new knowledge and to simplify it, for those whom she seeks to train up for the kingdom of heaven. She will not strive to combine fashionable amusements, or dissipation of thought, with her solemn and delightful obligations. She will labour as "ever in her Great Task-Master's Eye," to do. for the minds and souls of her children, that which none can perform as well as herself, which, if she neglects, may not be done at all, and if left undone, will be a loss, for which eternity must pay.-L. Sigourney's Letters to Mothers. ADVENTURE ON THE THAMES. It was on a fine sultry day, in the summer of 1821, that I was racing up the River Thames, in the command of the Ramsgate Steam Packet, Eagle, hoping to overtake our Margate competitors, the Victory, and Favourite steamers, and bringing them nearer to view as we rounded the points of the Reach of the river. It was in the midst of this excitement, that we encountered one of those sudden thunder squalls, so common in this country, and which passing rapidly off, with a heavy rain, leave behind them a strong and increasing northerly gale. I was looking out ahead, pleasing myself with the reflection that we were the fastest vessel against a head wind, and should certainly overtake our Margate friends; when upon entering Long Reach, about two miles below Purfleet, I saw a boat labouring with very little effect against the gale, and with a whole ebb-tide just making to add to their difficulties; in this boat were two ladies, in the close habit of the Society of Friends, evidently drenched with the heavy shower which had overtaken them. I was then a dashing, highspirited sailor; but I had always a secret admiration of the quiet demeanour of that Society, and occasionally had some of them passengers with me, always intelligent and inquiring, and always pleased with any information a seaman could extend to them. Well, here was a dilemma! To stop would spoil my chase, in which most of my passengers were as eager as myself; but to go on, and to pass two ladies in such a situation! I passed the word softly to the engineer; desired the mate to sheer alongside the boat carefully; threw the delighted rowers a rope, and before the passengers were fully aware that we had stopped the engines, the ladies were on board, the boat made fast astern, and the Eagle again flying up the Thames. I have those two persons strongly, nay, indelibly stamped upon my mind's eye. The one I had last assisted on board, still held my hand, as she thanked me, with dignified but beautiful expression: It is kind of thee, Captain, and we thank thee. We made no sign to thee; having held up our handkerchiefs to the other packets, we did not think we should succeed with thee. I assured them that I could not have passed them under such circumstances, and called the stewardess to take them below into the ladies' cabin and see to their comfort. They had been well cloaked, and had not suffered so much as I had anticipated. The gale had cleared away the rain, and in a very short time they came upon deck again; one of them was Mrs. Fry, and she never lost an opportunity of doing good. I saw her speaking to some of my crew, who were looking very serious as she offered them tracts, and some of them casting a side glance at me for my approval or otherwise. I had some little dislike to sects then, which I thank God left me in riper years, -but who could resist this beautiful, persuasive, and heavenly-minded woman. To see her, was to love her; to hear her, was to feel as if a guardian angel had bid you follow that teaching which could alone subdue the temptations and evils of this life, and secure a Redeemer's love in eternity! In her you saw all that was attractive in woman, lit up by the bright beams of philanthropy; devoting the prime of life, and health, and personal graces, to her Divine Master's service; and I feel assured that much of the success which attended her missions of mercy, was based upon that awe which such a presence inspired. It was something to possess a countenance which portrayed in every look, the overflowings of such a heart, and thus as a humble instrument in the hands of Divine Providence, she was indeed highly favoured among women. She told me that her companion, Mrs. Pryor, and herself had been down to Gravesend to take leave of the unfortunate women, (convicts,) on board a ship bound to the settlements, and gave me so touching a description of their behaviour, that I volunteered to take charge of any thing for her at any time, or render her any service in my power in my voyages. When about to land, her anxiety to make some pecuniary recompense was very great, but I would not allow her to do so. Mrs. Fry never forgot me when she came near our locality; I saw her from time to time; the earthly tabernacle failing, but the same spirit lighting up with animation her untiring energies. It was an honour to know her in this world; may we follow her to the society of the accepted and blessed in that which is to come. "K. B. MARTIN. Ramsgate, February, 1847." SLAVERY AND IGNORANCE. [Continued from page 15.] In South Carolina there is also a fund for the support of pauper schools; but this had become so useless, and was so disdained by its objects, that a late Governor of the State, in his annual message, recommended that it should be withdrawn from them altogether. Clarke, of Kentucky, declared, in his message to the Legislature, that "one-third of the adult population were unable to write their names;" and in the State of Tennessee, according to the last census, there were 58,531 of the same description of persons. Surely it would take more than five of these to make three freemen ; for the more a State has of them the less of intelligent freedom will there be in it. And if the schools in the slave States are compared with the schools in the free States, the deficiency in quality will be as great as the deficiency in number. During the last ten years I have had a most extensive correspondence with the intelligent friends of education in the slave States. They yearn for progress, but they cannot obtain it. They procure laws to be passed, but there is no one to execute them. They set forth the benefits and blessings of education, but they speak in a vacuum, and no one hears the appeal. If a parent wishes to educate his children, he must send them from home, and thus suffer a sort of bereavement, even while they live; or he must employ a tutor or governess in his family, which few are able to do. The rich may do it, but what becomes of the children of the poor? In cities the obstacles are less, but the number of persons resident in cities is relatively small. All this is the inevitable consequence of slavery, and it is as impossible for free, thorough, universal education, to co-exist with slavery, as for two bodies to occupy the same space at the same time. Slavery would abolish education if it should invade a free State; education would abolish slavery if it could invade a slave State. Destroying common education, slavery destroys the fruits of common education-the inventive mind, the practical talent, the power of adapting means to ends in the business of life. Yet, in many of the slave States there are Whence have come all the mechanical and beautiful paper systems of common-schools- scientific improvements and inventions which dead laws in the statute books-but the census have enriched the world with so many comforts, tells us how profitless they have been. In 1840, and adorned it with so many beauties, which toin the fifteen slave States and Territories, there day give enjoyments and luxuries to a common were only 201,085 scholars at the primary family in a New England village, which neither schools. In the same class of schools, in the Queen Elizabeth, of England, nor any of her free States, there were 1,626,082-eight times proud court, ever dreamed of, but a little more as many. New York alone had 502,367, or than two centuries ago? Among whom have two and a half times as many. The scholars in these improvements originated? All history the primary schools of Ohio alone outnumbered and experience affirm that they have come, and all those in the fifteen slave States and Territo- must come, from people among whom education ries by more than 17,000. In the slave States is most generous and unconfined. Increase the almost one-tenth part of the free white popu- constituency, if I may so speak, of developed lation, over twenty years of age, are unable to intellect, and you increase in an equal ratio the read and write. In the free States less than one chances of inventive, creative genius. From in one hundred and fifty; and at least four-fifths what part of our own country have come the of these are foreigners, who ought not to be in-application of steam to the propulsion of boats cluded in the computation. Many of the slave for commercial purposes, or of wheels for manuStates, too, have munificent school funds. Ken- facturing purposes? Where have the various tucky has one of more than a million of dollars, and almost infinite improvements been made, Tennessee of two millions-yet, in 1837, Gov. which have resulted in the present perfection. |