Popular Science Monthly/Volume 8/November 1875/Origin and Development of Engineering
By Sir JOHN HAWKSHAW, F. R. S.
TO those on whom the British Association confers the honor of presiding over its meetings the choice of a subject presents some difficulty. The presidents of sections give accounts of what is new in their departments; and essays on science in general, though desirable in the earlier years of the Association, would be less appropriate to-day. Past presidents have discoursed on many subjects, on the mind and on things beyond the reach of mind, and I have arrived at the conclusion that humbler themes will not be out of place on this occasion. I propose to say something of a profession to which my life has been devoted—a theme which cannot stand as high in your estimation as in my own, but which I have chosen because I ought to understand it better than any other. I propose to say something on its origin, its work, and kindred topics.
Rapid as has been the growth of the art of the engineer during the last century, we must, if we would trace its origin, seek among the earliest evidences of civilization. When settled communities were few and isolated, opportunities for the interchange of knowledge were scanty or wanting. The slowly accumulated results of the experience of a community were lost on its downfall. Inventions were lost and found again. The art of casting bronze over iron was known to the Assyrians, though it has only lately been introduced into modern metallurgy; and patents were granted in 1609 for processes connected with the manufacture of glass, which had been practised centuries before. An inventor in the reign of Tiberius devised a method of producing flexible glass, but the manufactory of the artist was totally destroyed in order to prevent the manufacture of copper, silver, and gold, from becoming depreciated.
In the long discussion which was held as to the practicability of making the Suez Canal, an early objection was brought against it that there was a difference of thirty-two and one-half feet between the level of the Red Sea and that of the Mediterranean. Laplace declared that such could not be the case, for the mean level of the sea was the same on all parts of the globe. Centuries before the time of Laplace the same objection had been raised against a project for joining the waters of these two seas. According to the old Greek and Roman historians, it was a fear of flooding Egypt with the waters of the Red Sea that made Darius, and in later times again Ptolemy, hesitate to open the canal between Suez and the Nile. Yet this canal was made and was in use some centuries before the time of Darius. Strabo tells us that the same objection, that the adjoining seas were of different levels, was made by his engineers to Demetrius, who wished to cut a canal through the Isthmus of Corinth some two thousand years ago. But Strabo dismisses at once this idea of a difference of level, agreeing with Archimedes that the force of gravity spreads the sea equally over the earth.
When knowledge in its higher branches was confined to a few, those who possessed it were called upon to perform various services for the communities to which they belonged; and we find mathematicians, and astronomers, painters, sculptors, and priests, called upon to perform the duties which now pertain to the profession of the architect and the engineer. As soon as civilization had advanced so far as to admit of the accumulation of wealth and power, then kings and rulers sought to add to their glory while living by the erection of magnificent dwelling-places, and to provide for their aggrandizement after death by the construction of costly tombs and temples.
The earliest buildings of stone to which we can assign a date, with any approach to accuracy, are the pyramids of Ghizeh. The genius for dealing with large masses in building did not pass away with the pyramid-builders in Egypt, but their descendants continued to gain in mechanical knowledge. The Romans, though they did not commonly use such large stones in their own constructions, carried oft the largest obelisks from Egypt and erected them at Rome, where more are now to be found than remain in Egypt.
It has sometimes been questioned whether the Egyptians had a knowledge of steel. It seems unreasonable to deny them this knowledge. Iron was known at the earliest times of which we have any record. It is often mentioned in the Bible, and in Homer; it is shown in the early paintings on the walls of the tombs at Thebes; it has been found in quantity in the ruined palaces of Assyria; and in the inscriptions of that country fetters are spoken of as having been made of iron, which is also so mentioned in connection with other metals as to lead to the supposition that it was regarded as a base and common metal. The quality of iron which is now made by the native races of Africa and India is that which is known as wrought-iron. Dr. Percy says the extraction of good malleable iron, directly from the ore, "requires a degree of skill very far inferior to that which is implied in the manufacture of bronze." The supply of iron in India as early as the fourth and fifth centuries seems to have been unlimited. In the temples of Orissa iron was used in large masses as beams or girders in roof-work in the thirteenth century, and India well repaid any advantage which she may have derived from the early civilized communities of the West if she were the first to supply them with iron and steel. If we look still farther to the East, China had probably knowledge of the use of metals as soon as India, and, moreover, had a boundless store of iron and coal. A great future is undoubtedly in store for that country; but can the race who now dwell there develop its resources, or must they await the aid of an Aryan race? The art of extracting metals from the ore was practised at a very early date in this country. The Romans worked iron extensively in the Weald of Kent, as we assume from the large heaps of slag containing Roman coins which still remain there. Coal, which was used for ordinary purposes in England as early as the ninth century, does not appear to have been largely used for iron-smelting until the eighteenth century, though a patent was granted for smelting iron with coal in the year 1611. The use of charcoal for that purpose was not given up until the beginning of this century, since which period an enormous increase in the mining and metallurgical industries has taken place; the quantity of coal raised in the United Kingdom in 1873 having amounted to 127,000,000 tons, and the quantity of pig-iron to upward of 6,500,000 tons.
The early building energy of the world was chiefly spent on the erection of tombs, temples, and palaces. While in Egypt, as we have seen, the art of building in stone had 5,000 years ago reached the greatest perfection, so in Mesopotamia the art of building with brick, the only available material in that country, was in an equally advanced state some ten centuries later. The practice of building great pyramidal temples seems to have passed eastward to India and Burmah, where it appears in buildings of a later date, in Buddhist topes and pagodas; marvels of skill in masonry, and far surpassing the old brick mounds of Chaldea in richness of design and in workmanship. Egypt was probably far better irrigated in the days of the Pharaohs than it is now; and Lake Mœris, of which the remains have been explored by M. Linant, was a reservoir made by one of the Pharaohs, and supplied by the flood-waters of the Nile. It was 150 square miles in extent, and was retained by a bank or dam 60 yards wide and 10 high, which can be traced for a distance of 13 miles. This reservoir was capable of irrigating 1,200 square miles of country. No work of this class has been undertaken on so vast a scale since, even in these days of great works. The springs of knowledge which had flowed so long in Babylonia and Assyria were dried up at an early period; but Egypt remained the fountain-head whence knowledge flowed to Greece and Rome. The early constructive works of Greece, till about the seventh century b. c, form a strong contrast to those of its more prosperous days. Commonly called Pelasgian, they are more remarkable as engineering works than admirable as those which followed them were for architectural beauty. Walls of huge unshapely stones—admirably fitted together, however—tunnels, and bridges characterize this period. In Greece, during the few and glorious centuries which followed, the one aim in all construction was to please the eye, to gratify the sense of beauty; and in no age was that aim more thoroughly and satisfactorily attained.
In these days, when sanitary questions attract each year more attention, we may call to mind that twenty-three centuries ago the city of Agrigentum possessed a system of sewers, which on account of their large size was thought worthy of mention by Diodorus. This is not, however, the first record of towns being drained. The well-known Cloaca Maxima, which formed part of the drainage system of Rome, was built some two centuries earlier, and great vaulted drains passed beneath the palace-mounds of unburnt brick at Nimroud and Babylon, and possibly we owe the preservation of many of the interesting remains found in the brick-mounds of Chaldea to the very elaborate system of pipe drainage discovered in them and described by Loftus. While Pelasgian art was being superseded in Greece, the city of Rome was founded, in the eighth century before our era; and Etruscan art in Italy, like the Pelasgian art in Greece, was slowly merged in that of an Aryan race.
It would be impossible for me to do justice to even a small part of the engineering works which remain to this day as monuments of the skill, the energy, and ability, of the great Roman people. War, with all its attendant evils, has often indirectly benefited mankind. In the sieges which took place during the wars of Greece and Rome, the inventive power of man was taxed to the utmost to provide machines for attack and defense. The ablest mathematicians and philosophers were pressed into the service, and helped to turn the scale in favor of their employers. The world has to regret the loss of more than one who, like Archimedes, fell slain by the soldiery while applying the best scientific knowledge of the day to devising means of defense during the siege. The necessity for roads and bridges for military purposes has led to their being made where the stimulus from other causes was wanting; and means of communication and the interchange of commodities, so essential to the prosperity of any community, have thus been provided. Such was the case under the Roman Empire. So, too, in later times, the ambition of Napoleon covered France and the countries subject to her with an admirable system of military roads. So, again, in this country, it was the rebellion of 1745, and the want felt of roads for military purposes, which first led to the construction of a system of roads in it unequaled since the time of the Roman occupation. And lastly, in India, in Germany, and in Russia, more than one example could be pointed out where industry will be benefited by railways which have originated in military precautions rather than in commercial requirements.
But to return to Rome. Roads followed the tracks of her legions into the most distant provinces of the empire. Three hundred and seventy-two great roads are enumerated, together more than 48,000 miles in length, according to the itinerary of Antoninus. The water-supply of Rome during the first century of our era would suffice for a population of 7,000,000, supplied at the rate at which the present population of London is supplied. This water was conveyed to Rome by nine aqueducts; and in later years the supply was increased by the construction of five more aqueducts. Three of the old aqueducts have sufficed to supply the wants of the city in modern times. These aqueducts of Rome are to be numbered among her grandest engineering works. Time will not admit of my saying any thing about her harbor works and bridges, her basilicas and baths, and numerous other works in Europe, in Asia, and in Africa.
In the fourth and succeeding centuries the barbarian hordes of Western Asia, people who felt no want of roads and bridges, swept over Europe to plunder and destroy. With the seventh century began the rise of the Mohammedan power, and a partial return to conditions apparently more favorable to the progress of industrial art, when widespread lands were again united under the sway of powerful rulers. Still, few useful works remain to mark the supremacy of the Mohammedan power at all comparable to those of the age which preceded its rise.
A great building-age began in Europe in the tenth century, and lasted through the thirteenth. While the building of cathedrals progressed on all sides in Europe, works of a utilitarian character, which concern the engineer, did not receive such encouragement, excepting perhaps in Italy. In India, under the Moguls, irrigation works, for which they had a natural aptitude, were carried on during these centuries with vigor, and more than one emperor is noted for the numerous great works of this nature which he carried out.
It is frequently easier to lead water where it is wanted than to check its irruption into places where its presence is an evil, often a disaster. For centuries the existence of a large part of Holland has been dependent on the skill of man. How soon he began in that country to contest with the sea the possession of the land we do not know, but early in the twelfth century dikes were constructed to keep back the ocean. To the practical knowledge acquired by the Dutch, whose method of carrying out hydraulic works is original and of native growth, much of the knowledge of the present day in embanking, and draining, and canal-making, is due. While the Dutch were acquiring practical knowledge in dealing with water, and we in Britain, among others, were benefiting by their experience, the disastrous results which ensued from the inundations caused by the Italian rivers of the Alps gave a new importance to the science of hydraulics. Some of the greatest philosophers of the seventeenth century—among them Torricelli, a pupil of Galileo—were called upon to advise and to superintend engineering works; nor did they confine themselves to the construction of preventive works, but thoroughly investigated the condition pertaining to fluids at rest or in motion, and gave to the world a valuable series of works on hydraulics and hydraulic engineering, which form the basis of our knowledge of these subjects at the present day.
The impulse given to road-making in the early part of the last century soon extended to canals, and means for facilitating locomotion and transport generally. Tramways were used in connection with mines at least as early as the middle of the seventeenth century, but the rails were, in those days, of wood. The first iron rails are said to have been laid in this country as early as 1738, after which time their use was gradually extended, until it became general in mining districts. By the beginning of this century the great ports of England were connected by a system of canals; and new harbor-works became necessary, and were provided to accommodate the increase of commerce and trade, which improved means of internal transport had rendered possible. But it was not until the steam-engine, improved and almost created by the illustrious Watt, became such a potent instrument, that engineering works to the extent they have since been carried out became possible or necessary. But, while Watt had gained a world-wide, well-earned fame, the names of those men who have provided the machines to utilize the energies of the steam-engine are too often forgotten. Of their inventions the majority of mankind know little. They worked silently at home, in the mill, or in the factory, observed by few. Indeed, in most cases these silent workers had no wish to expose their work to public gaze. How long in the silent night the inventors of these machines sat and pondered; how often they had to cast aside some long-sought mechanical movement and seek another and better arrangement of parts, none but themselves could ever know. They were unseen workers, who succeeded by rare genius, long patience, and indomitable perseverance.
More ingenuity and creative mechanical genius is perhaps displayed in machines used for the manufacture. of textile fabrics than by those used in any other industry. It was not until late in historical times that the manufacture of such fabrics became established on a large scale in Europe. Linen was worn by the old Egyptians, and some of their linen mummy-cloths surpass in fineness any linen fabrics made in later days. The Babylonians wore linen also and wool, and obtained a wide-spread fame for skill in workmanship and beauty in design. In this country wool long formed the staple for clothing. Silk was the first rival, but its costliness placed it beyond the reach of the many. To introduce a new material or improved machine into this or other countries a century or more ago was no light undertaking. Inventors and would-be benefactors alike ran the risk of loss of life. Loud was the outcry made in the early part of the eighteenth century against the introduction of Indian cottons and Dutch calicoes. Until 1738, in which year the improvements in spinning-machinery were begun, each thread of worsted or cotton-wool had been spun between the fingers, in this and all other countries, Wyatt, in 1738, invented spinning by rollers instead of fingers, and his invention was further improved by Arkwright. In 1770 Hargreaves invented the spinning-jenny, and Crompton the mule in 1775, a machine which combined the advantages of the frames of both Hargreaves and Arkwright. In less than a century after the first invention by Wyatt, double mules were working in Manchester with over 2,000 spindles. Improvements in machines for weaving were begun at an earlier date. In 1579 a ribbon-loom is said to have been invented at Dantzic, by which from four to six pieces could be woven at one time, but the machine was destroyed and the inventor lost his life. In 1800 Jacquard's most ingenious invention was brought into use, which, by a simple mechanical operation, determines the movements of the threads which form the pattern in weaving. But the greatest improvement in the art of weaving was wrought by Cartwright's discovery of the power-loom, which led eventually to the substitution of steam for manual labor, and enabled a boy with a steam-loom to do fifteen times the work of a man with a hand-loom. For complex ingenuity few machines will compare with those used in the manufacture of lace and bobbin net. Hammond, in 1768, attempted to adapt the stocking-frame to this manufacture, which had hitherto been conducted by hand. It remained for John Heathcoat to complete the adaptation in 1809, and to revolutionize this branch of industry, reducing the cost of its produce to one-fortieth of what the cost had been before Heathcoat's improvements were effected. Time would fail me if I were to attempt to enumerate one tithe of these rare combinations of mechanical skill; and, indeed, no one will ever appreciate the labor and supreme mental effort required for their construction who has not himself seen them and their wondrous achievements.
Steamboats, the electric telegraph, and railways, are more within the cognizance of the world at large, and the progress that has been made in them in little more than one generation is better known and appreciated. It is not more than forty years since one of our scientific men, and an able one too, declared at a meeting of this Association that no steamboat would ever cross the Atlantic; founding his statement on the impracticability, in his view, of a steamboat carrying sufficient coal, profitably, I presume, for the voyage. Like most important inventions, that of the steamboat was a long time in assuming a form capable of being profitably utilized, and, even when it had assumed such a form, the objections of commercial and scientific men had still to be overcome. The increase in the number of steamboats since the time when the Sirius first crossed the Atlantic has been very great. Whereas in 1814 the United Kingdom only possessed two steam-vessels, of together 456 tons burden, in 1872 there were on the register of the United Kingdom 3,662 steam-vessels, of which the registered tonnage amounted to over a million and a half of tons, or to nearly half the whole steam tonnage of the world, which did not at that time greatly exceed three million tons. As the number of steamboats has largely increased, so also gradually had their size increased until it culminated in the hands of Brunei in the Great Eastern. A triumph of engineering skill in ship-building, the Great Eastern has not been commercially so successful. In this, as in many other engineering problems, the question is not how large a thing can be made, but how large, having regard to other circumstances, it is proper at the time to make it.
A distinguished member of this Association, Mr. Froude, has now for some years devoted himself to investigations carried on with a view to ascertain the form of vessel which will offer the least resistance to the water through which it must pass. So many of us in these days are called upon to make journeys by sea as well as by land that we can well appreciate the value of Mr. Froude's labors, so far as they tend to curtail the time which we must spend on our ocean-journeys; and we should all feel grateful to him if from another branch of his investigations, which relates to the rolling of ships, it would result that the movement in passenger-vessels could be reduced.
There is no more remarkable instance of the rapid utilization of what was at first regarded as a mere scientific idea than the adoption and extension of the electric telegraph. Those who read Odier's letter written in 1773, in which he made known his idea of a telegraph which would enable the inhabitants of Europe to converse with the Great Mogul little thought that in less than a century a conversation between persons at points so far distant would be possible. Still less did those, who saw in the following year messages sent from one room to another by Lesage in the presence of Frederick of Prussia, realize that they had before them the germ of one of the most extraordinary inventions among the many that will render this century famous. I should weary you were I to follow the slow steps by which the electric telegraph of to-day was brought to its present state of efficiency; but yet within how short a period of time has all the wonderful progress been achieved! How incredulous the world a few years ago would have been if then told of the marvels which in so short a space of time were to be accomplished by its agency! It is not long ago—1823—that Mr. (now Sir Francis) Ronald, one of the early pioneers in this field of science, published a description of an electric telegraph. He communicated his views to Lord Melville, and that nobleman was obliging enough to reply that the subject should be inquired into; but before the nature of Sir Francis Ronald's suggestions could be known, except to a few, that gentleman received a reply from Mr. Barrow that "telegraphs of any kind were then wholly unnecessary, and that no other than the one then in use would be adopted;" the one then in use being the old semaphore, which, crowning the tops of hills between London and Portsmouth, seemed perfection to the Admiralty of that day. The telegraphic system of the world comprises almost a complete girdle round the earth; and it is probable that the missing link will be supplied by a cable between San Francisco, in California, and Yokohama, in Japan. How resolute and courageous those who engaged in submarine telegraphy have been will appear from the fact that, though we have now 50,000 miles of cable in use, to get at this result nearly 70,000 miles were constructed and laid.
Of railways the progress has been enormous; but I do not know that in a scientific point of view a railway is so marvelous in its character as the electric telegraph. The results, however, of the construction and use of railways are more extensive and wide spread, and their utility and convenience brought home to a larger portion of mankind. The British Association is peripatetic, and without railways its meetings, if held at all, would, 1 fear, be greatly reduced in numbers. Moreover, you have all an interest in them; you all demand to be carried safely, and you insist on being carried fast. I shall not enter on a history of the struggles which preceded the opening of the first railway. They were brought to a successful-issue by the determination of a few able and far-seeing men. The names of Thomas Gray and Joseph Sandars, of William James and Edward Pease, should always be remembered in connection with the early history of railways, for it was they who first made the nation familiar with the idea. There is no fear that the name of Stephenson will be forgotten, whose practical genius made the realization of the idea possible. Railways add enormously to the national wealth. More than twenty-five years ago it was proved, to the satisfaction of a committee of the House of Commons, that the Lancashire & Yorkshire Railway effected a saving to the public using the railway of more than the whole amount of the dividend which was received by the proprietors. These calculations were based solely on the amount of traffic carried by the railway and on the difference between the railway rate of charge and the charges by the modes of conveyance anterior to railways. No credit whatever was taken for the saving of time, though in England preeminently time is money. Considering that railway charges on many items have been considerably reduced since that day, it may be safely assumed that the railways in the British Islands now produce, or rather save to the nation, a much larger sum annually than the gross amount of all the dividends payable to the proprietors, without at all taking into account the benefit arising from the saving in time. The benefits under that head defy calculation, and cannot with any accuracy be put into money; but it would not be at all over-estimating this question to say that in time and money the nation gains at least what is equivalent to ten per cent, on all the capital expended on railways. It follows that, whenever a railway can be made at a cost to yield the ordinary interest of money, it is in the national interest that it should be made. Further, that, though its cost might be such as to leave a smaller dividend than that to its proprietors, the loss of wealth to so small a section of the community will be more than supplemented by the national gain, and therefore there may be cases where a government may wisely contribute in some form to undertakings which, without such aid, would fail to obtain the necessary support. And so some countries—Russia, for instance—to which improved means of transport are of vital importance, have wisely, in my opinion, caused lines to be made which, having regard to their own expenditure and receipts, would be unprofitable works, but in a national point of view are or speedily will be highly advantageous.
A question more important probably in the eyes of many—safety of railway-traveling—may not be inappropriate. At all events, it is well that the elements on which it depends should be clearly understood. It will be thought that longer experience in the management of railways should go to insure greater safety, but there are other elements of the question which go to counteract this in some degree. The safety of railway-traveling depends on the perfection of the machine in all its parts, including the whole railway, with its movable plant, in that term; it depends also on the nature and quantity of traffic; and, lastly, on human care and attention. With regard to what is human, it may be said that so many of these accidents as arise from the fallibility of men will never be eliminated until the race be improved. The liability to accident will also increase with the speed, and might be reduced by slackening that speed. It increases with the extent and variety of the traffic on the same line. The public, I fear, will rather run the risk than consent to be carried at a slower rate. The increase in extent and variety of traffic is not likely to receive any diminution; on the contrary, it is certain to augment. I should be sorry to say that human care may not do something, and I am not among those who object to appeals through the press and otherwise to railway companies, though sometimes perhaps they may appear in an unreasonable form. I see no harm in men being urged in every way to do their utmost in a matter so vital to many. It is practicable, by certain corrections of the official returns, to make some sort of comparison between the accidents in the earlier days of our own railways and. the accidents occurring at a later date. I have endeavored to make these corrections, and I believe the results arrived at may be taken as fairly accurate. From the figures it appears that the passenger mileage has doubled between 1861 and 1873; and at the rate of increase between 1870 and 1873 it would become double what it was in 1873 in twelve years from that time—namely, in 1885. The number of passengers has doubled between 1864 and 1873, and at the rate of increase between 1870 and 1873 it would become double what it was in 1873 in eleven and a half years, or in 1 885. Supposing no improvement had been effected in the working of railway-traffic, the increase of accidents should have borne some proportion to the passenger mileage, multiplied by the proportion between the train mileage and the length of line open, as the number of trains passing over the same line of rails would tend to multiply accidents in an increasing proportion, especially where the trains run at different speeds. The number of accidents varies considerably from year to year, but, taking two averages of ten years each, it appears that the proportion of deaths of passengers from causes beyond their control to passenger miles traveled in the ten years ending December 31, 1873, was only two-thirds of the same proportion in the ten years ending December 31, 1861. The limit of improvements will probably be reached before long, and the increase of accidents will depend on the increase of traffic, together with the increased frequency of trains. Up to the present time the improvements appear to have kept pace with the increase of traffic and of speed, as the slight increase in the proportion of railway accidents to passenger miles is probably chiefly due to a larger number of trifling bruises being reported now than formerly. I believe it was a former president of the Board of Trade who said to an alarmed deputation, who waited upon him on the subject of railway traveling, that he thought he was safer in a railway-carriage than anywhere else. If he gave any such opinion, he was not far wrong, as is sufficiently evident when it can be said that there is only one passenger injured in every four million miles traveled, or that, on an average, a person may travel 100,000 miles each year for forty years, and the chances be slightly in his favor of his not receiving the slightest injury.
A pressing subject of the present time is the economy of fuel. Members of the British Association have not neglected this momentous question. Many cases of waste arise from the existence of old and obsolete machines, of bad forms of furnaces, of wasteful grates, existing in most dwelling-houses; and these are not to be remedied at once, for not every one can afford, however desirable it might be, to cast away the old and adopt the new. In looking uneasily to the future supply and cost of fuel, it is, however, something to know what may be done even with the application of our present knowledge; and, could we apply it universally to-day, all that is necessary for trade and comfort could probably be as well provided for by one-half the present consumption of fuel; and it behooves those who are beginning to build new mills, new furnaces, new steamboats, or new houses, to act as though the price of coal which obtained two years ago had been the normal and not the abnormal price.
There was in early years a battle of the gauges, and there is now a contest about guns; but your time will not permit me to say much on their manufacture. Here, again, the progress made in a few years has been enormous, and in contributing to it, two men—Sir William Armstrong and Sir Joseph Whitworth, both civil engineers—in this country, at all events, deservedly stand foremost. Docks and harbors I have no time to mention, for it is time this long and, I fear, tedious address should close.
"Whence and whither" is the aphorism which leads us away from present and plainer objects to those which are more distant and obscure; whether we look backward or forward our vision is speedily arrested by an impenetrable veil. On the subject I have chosen you will probably think I have traveled backward far enough. I have dealt to some extent with the present. The retrospect, however, may be useful to show what great works were done in former ages. Some things have been better done than in those earlier times, but not all. In what we choose to call the ideal we do not surpass the ancients. Poets and painters and sculptors were as great in former times as now; so, probably, were the mathematicians. In what depends on the accumulation of experience we ought to excel our forerunners. Engineering depends largely on experience; nevertheless, in future times whenever difficulties shall arise, 'or works have to be accomplished for which there is no precedent, he who has to perform the duty may step forth from any of the walks of life, as engineers have not unfrequently hitherto done. The marvelous progress of the last two generations should make every one cautious of predicting the future. Of engineering works it may be said that their practicability or impracticability is often determined by other elements than the inherent difficulty in the works themselves. Greater works than any yet achieved remain to be accomplished—not, perhaps, yet awhile. Society may not yet require them; the world could not at present afford to pay for them. The progress of engineering works, if we consider it, and the expenditure upon them, has already in our time been prodigious. One hundred and sixty thousand miles of railway alone, put into figures at £20,000 a mile, amounts to £3,200,000,000 sterling; add 400,000 miles of telegraph at £100 a mile, and £100,000,000 more for sea-canals, docks, harbors, water and sanitary works constructed in the same period, and we get the enormous sum of £3,340,000,000 sterling expended in one generation and a half on what may undoubtedly be called useful works. The wealth of nations may be impaired by expenditure on luxuries and war; it cannot be diminished by expenditure on works like these.
As to the future, we know we cannot create a force; we can, and no doubt shall, greatly improve the application of those with which we are acquainted. What we called inventions can do no more than this, yet how much every day is being done by new machines and instruments! The telescope extended our vision to distant worlds. The spectroscope has far outstripped that instrument, by extending our powers of analysis to regions as remote. Postal deliveries were and are great and able organizations, but what are they to the telegraph? Need we try to extend our vision into futurity farther? Our present knowledge, compared with what is unknown even in physics, is infinitesimal. We may never discover a new force—yet, who can tell?