CHAP. V. Of the Formation of Canals. 3526. Though the subject of canals is not included in that of agriculture, yet it is so intimately connected with territorial improvement, that it would be improper in a work of this description to pass it over. Canals of any extent are never the work of an individual, but of public bodies, constituted and empowered by public acts; but it is of importance to individuals to know the sort of effect which a canal passing through their property may have, both on its appearance and value; not merely as a medium of conveyance, but as a source of population, of water for irrigation or mills, or the use of stock, and even as an object of ornament. For this purpose we shall submit some remarks on the utility of canals, the choice of lines, the powers granted to canal companies, and the mode of execution. SECT. I. Utility of Navigable Canals. 3527. Good roads, canals, and navigable rivers, Dr. Smith observes (Wealth of Nations, i. 229), by diminishing the expense of carriage, put the remote parts of the country more nearly upon a level with those in the neighborhood of large towns; and on that account they are the greatest of all improvements. They encourage the cultivation of the remote parts, which must always be the most extensive circle of the country. They are advantageous to towns, by breaking down the monopoly of the country in its neighborhood, and they are advantageous to all parts of the country; for though they introduce some rival commodities into the old markets, they open many new markets to its produce. "All canals," says an intelligent writer on this subject (See Phillips's General History of Inland Navigation, Introd.) " may be considered as so many roads of a certain kind, on which one horse will draw as much as thirty horses on ordinary turnpike roads, or on which one man alone will transport as many goods as three men and eighteen horses usually do on common roads. The public would be great gainers were they to lay out upon the making of every mile of a canal twenty times as much as they expend upon a mile of turnpike road; but a mile of canal is often made at a less expense than the mile of turnpike; consequently there is a great inducement to multiply the number of canals." 3528. General arguments in favor of canals are superseded by the rapidly improving and thriving state of the several cities, towns, and villages, and the agriculture also near to most of the canals of the kingdom, the immense number of mines of coal, iron, limestone, &c. and great works of every kind to which they have been conducted, and to which a large portion of them owe their rise, are their best recommendation. In short, it may be concluded, that no canal can be completed and brought into use, but the inhabitants and the agriculture of the district will shortly feel great benefit from it, whatever may be the result to the proprietors. 3529. The great advantages of canals as means of transport results from the weight which may be moved along by a small power. The velocity with which boats can be drawn along a canal is confined within very narrow limits, owing, as Edgeworth has observed, to the nature of the resistance to which they are exposed; this resistance increasing in a geometrical proportion, as the squares of the velocity with which the moving body is impelled. Whereas on roads or railways, an increase of velocity requires only an arithmetical increase of power; or, in other words, to draw a boat with ten times a given velocity, would require a hundred times as much power as was requisite to draw it with that given velocity. Whereas, to draw a carriage on a road or railway with ten times a given velocity, would require only ten times the given power. For this reason, however advantageous canals may have been found, for transporting heavy loads, they will be found upon trial inferior to roads in promoting expedition. 3530. Canals appear to have been first made in Egypt. Though less attended to by the Romans than roads, yet they formed some in this country near Lincoln and Peterborough. China is remarkable for its canals, and there are many in Hindostan. In Russia there are some and especially in Sweden; one or two in Denmark; some in Germany, and a great many in Holland. The canal of Burgundy in France was commenced under Henry IV. and that of Languedoc finished by Riquet, the Brindley of France, under Louis XIV. Some attempts have been made to form canals in the hilly country of Spain, and a great many excellent ones are executed in America. 3531. Navigable canals in Britain took their rise between 1755 and 1760, by the Sankey Brook Company in Lancashire; but the great impulse was given by the duke of Bridgewater about 1757; when he first commenced, under the direction of Brindley, the canal between his coal-works at Worsley and Salford. The duke of Bridgewater has, in consequence, not improperly been called the father of canals in England; while his engincer, Brindley, by his masterly performances on the duke of Bridgewater's canal, altered and extended as the scheme thereof was by the three subsequent acts of parlia ment, has secured to himself, and will it should seem (from a comparison of the great features, and minutiae of execution in this the first canal, with most others in this country, even of the latest construction,) long continue to hold that rank among the English engineers, to which Riquet seems entitled among foreigners. 3532. Since the duke of Bridgewater's time the extension of canals in the British isles has been rapid. A number of scientific engineers have arisen, of whom we need only mention Smeaton, Rennie, and Telford, and point to the Caledonian canal. SECT. II. Of discovering the most eligible Rout for a Line of Canal. 3533. The first object when the idea of a canal is determined on by a few landed proprietors, is the choice of a skilful and experienced engineer. Such an artist should undoubtedly possess a considerable degree of mathematical knowledge. Calculations, of which some are of the most abstruse and laborious kind, will frequently occur; and he should, therefore, be well acquainted with the principles on which all calculations are founded, and by which they are to be rightly applied in practice. An engineer should also have studied the elements of most or all of the sciences immediately connected with his profession; and he should particularly excel in an acquaintance with the various branches of mechanics, both theoretical and practical. His knowledge should comprehend whatever has been written or done by other engineers, and he should have information in every department of his office, from an accurate examination of the most considerable works that have been executed in all the various circumstances that are likely to occur. It is necessary that he should be a ready and correct, if not a finished, draughtsman. He should also be conversant with the general principles of trade and commerce; with the various operations and improvements in agriculture; with the interests and connection of the different owners and occupiers of land, houses, mills, &c.; and with all the general laws and decisions of courts, pertaining to the objects connected with his profession. By an extensive acquaintance with the disposition, inclination, and thickness of the various strata of matter which compose the soil or land of the British islands, he will be able to avoid many errors incident to those who are destitute of this knowledge. As the last, though not the least, of these qualifications of an engineer, which we shall enumerate, he should be a man of strict integrity. 3534. A proper engineer being fixed upon, the adventurers should not tie him down too closely, by restrictions as to time, but allow him leisure to consider, digest, and revise again and again, the different projects and ways, which will naturally in most instances present themselves to him in an extensive and thorough investigation, The engineer should be allowed to choose and employ the most competent assistants, and to call in and occasionally to consult the opinions of eminent or practical men, as land-surveyors, agents of the neighboring landed property, the principal and most expert commercial men of the district and who are best acquainted with its trade and wants, any eminent miners, &c. &c.; and such men the engineer should be authorised liberally, and at once to remunerate for their services and intelligence. Previous to the beginning of any minute survey or system of levelling, the engineer ought to visit personally, and endeavour to make a just estimate, and preserve memorandums of all the objects within the district under consideration; as of the trade and importance of all the towns likely to be affected by the undertaking; of all mines of coal, iron, &c. ; quarries of limestone, freestone, slate, &c.; or the situation where such can be found; of all the manufactories of heavy and cumbrous goods, and other extensive works; and generally of every thing likely to furnish tonnage for a canal. The most eligible rout for a canal being settled in the engineer's mind, he will then proceed to make a rough calculation of the quantity of goods of each different kind which may be expected to pass upon the line in a given time; he will also examine all the canals and rivers which the proposed canal is to con nect with, and ascertain the widths and depths thereof, the sizes of their locks, and of the vessels usually navigating them. 3535. The dimensions, number, and kind of locks or inclined planes, length of levels, &c. may now be determined on, and how far railways or branch canals or roads may be connected with the main line. Many engineers, and especially Fulton, have warmly advocated the formation of small canals. On this subject, Chapman, a most judicious artist observes, "that the system of small canals is particularly eligible in all countries where limestone, coal, iron ore, lead, and other ponderous articles, not liable to damage from being wet, or likely to be stolen, are the objects chiefly to be attended to; and where the declivity of the country runs transversely to the course of the canal, which will generally be the case along the side of mountains, at an elevation above the regular ground at their feet. In those situations, the great falls or inclined planes may be made at the forks of rivers, so that the upper levels may branch up both the vales, and thus give the most extended communication. A situation suited for those canals will often be found in countries that are not absolutely mountainous, but where the ground regularly declines towards the vales or large rivers." 3536. A rough section of the proposed line will enable the engineer to see the places of the heights and breadths of the various summits, or ranges of high land that are to be passed, and whether any two or more adjacent ones can be connected by a long summit level, without deserting any considerable town or point of trade, which will diminish the difficulties of supplying the canal with water, as every such junction of summits preserves the water of two lockages, beside presenting so many more points at which the canal can be supplied with water, from springs and rivulets above its level, or where, in less favorable situations, the same can be collected in a lower level to be pumped up. From one end of the proposed summit level it will be right now to proceed with the survey, tracing the level accurately and marking the same by pegs or stakes, that will last for some time, and be known by the surveyor, who is to follow and make a plan of the line; the levels being frequently transferred to what are called bench marks, upon the trunk of a tree, a large post, or a building, the same being noted so particularly in the field or survey book, that they may be readily found for years afterwards. We suppose the engineers, by this time, to have settled the rise that each lock should have, according to the dimensions adopted for the canal, the probable supply of water on the summit, and other circumstances; the summit level will be traced as above, till the proper place occurs for making a fall of two or more locks, at about 100 yards, or a little more from each other; and the places of these falls being marked, the level is again to be pursued and traced from the bottom of them, and marked out as before, till the opportunity occurs for another pair or more of locks, or till some obstacle, as a gentleman's park, houses, gardens, orchards, mills, roads, &c. present themselves at a distance; when it will be proper, after transferring the level arrived at to a proper and permanent mark, to proceed forwards, and to examine and well consider the different ways and levels, if more than one of such present themselves, by which the obstacle can be passed. From the most confined part of the course for the canal, owing to the obstacle, it will be right to level back, till the former work is met, and to determine the most eligible mode of bringing the two levels together, upon the principles before stated; if they can be applied, either by adding another lock, or taking one from any of the sets of them which had been before marked out, as occasion may require, and marking out the new levels thereby occasioned the line between the summit and the first obstacle, or confined part of the course, being thus adjusted, a new point of departure is to be taken from such obstacle, and the level pursued as before, till the fall for a pair or more locks can be gained, at the proper distance from each other. In this way, the patience, perseverance, and abilities of the engineer must be exercised, until a practicable line of some length is obtained, and staked out; when the assistant land-surveyor must follow, and make a correct and particular plan of the line of the several proposed locks, embankments, tunnels, &c. upon the same, and of the several fields, or pieces of land through which it passes, or that come within 100 or 150 yards of it in any part it will likewise be the business of the surveyor to ascertain, with the utmost care, the boundary of every parish and township, what county each is in, the proper names of the owners and occupiers of every piece of land in each, however small, upon or within that distance of the line, with reference to the same upon his plan; and to describe correctly all public and private roads and paths that cross or intersect the line, and to and from what places they lead; the course of all brooks or streams of water, and particularly such as lead to and contribute to the supply of any mill: the situation of the houses and towns upon the line, or within some miles of it, should also be determined; the nearer they are the greater accuracy will be necessary. A complete plan of the line, and all the projected collateral cuts, feeders, reservoirs, &c. being finished, the engineer will enter on a most careful revisal of the whole scheme, with this plan in his hand; on which all the places where culverts or drains will be required, are to be marked, as also the proper places for the bridges, and the necessary alterations of the roads and paths, which will be cut off by the canal, so that the public will not be inconvenienced and turned long distances round about, and still, that as few bridges as possible, and those in the least expensive places, may be erected. In some instances new channels will require to be cut for brooks and water-courses, to a considerable extent, in order to save culverts, or bring them to the most desirable spots. For proper security against accidental errors, the whole of the levelling should now be gone over again, and the several bench marks compared, and renewed with the utmost care by the engineer's assistants, while he is proceeding with the necessary inquiries and calculations, for an estimate of the whole expense of the undertaking. 3537. The supplying of a canal with water, in a great number of instances, occasions no inconsiderable share of the whole expense, either in the first cost of mills or streams of water, in land for, and labor in, constructing reservoirs, engines to pump water, &c.; or annually ever afterwards, in the fuel for, and repairing of engines, hire of water from mills in dry seasons, &c.; this subject should, therefore, employ the most sedulous atten tion of the engineer, both to make the most economical use of what streams he finds, to procure other supplies of water at the least expense, but above all, to secure an abundant sufficiency. The dimensions and heights of the locks, and breadth of the canal being settled, an accurate calculation made of the quantity of water required to fill a lock; and, with the largest probable number of boats that will pass in a day, the quantity required daily in every part of the canal; this, with a due allowance for the evaporation, from the surface of the whole canal and its reservoirs, and for the soakage that will take place into the banks, however well they are constructed; will show the number of locks full of water that will be required, from all the different sources. 3538. In estimating the expense of all such works, the lengths and solid contents of the several embankments, and the distance from which the stuff or soil must be fetched for the same; the lengths and dimensions of all the deep cuttings, and the distance to which the stuff must be removed; the lengths of the tunnels, and number and depths of the several shafts or tunnel pits will be necessary; the lengths or headings of soughs that will be wanted to drain the tunnelling work; these, and all the great variety of other works, some of which we have already mentioned, and others we shall have occasion to mention in the sequel, being particularly stated, and prices affixed to each species of work and kind of material; (and these prices ought not to be below the current prices of the best articles at the time, but due allowance should also be made for the advance of prices, which will take place during the advancement of the work ;) the total probable expense, with a due allowance for contingencies, will be thus obtained, on which the engineer will prepare his general report and estimate, to be laid, with the plan, before a meeting of the adventurers or proposed proprietors. SECT. III. Of the Powers granted to Canal Companies by Government. 3539. As a canal must pass through a great variety of private property, and necessarily affect different individuals in very opposite ways, considerable powers are requisite to carry it into execution. The first step to attain these is the appointment of a solicitor, and an application to parliament for an act of incorporation and regulation. 3540. A canal bill contains numerous clauses; but the following may be considered as the heads of the most general. Regulations as to raising money by shares or other wise. Election of committees and general meetings of proprietors. Enactments relative to purchasing lands, &c. Powers for erecting wharfs, and enforcing certain equitable rates of wharfage. Tolls, or rates of tonnage, with exemptions, if any. Fixing mile-stones, for regulating distances and tonnage. Removing the surface-soil, and clamping it, for the purpose of being again laid on the surface of the exterior banks of the canal; or for other purposes. Forming watering places for cattle or irrigation. Power to make bye-laws. Form of conveying land to the canal company. Regulations as to depositing plans of the canal, and making variations from them, &c. 3541. The act of parliament for a canal being passed, and therein the time and place for the first meeting of the subscribers or proprietors thereof being fixed; the first business of such meeting will be the election of a general committee of management, consisting of the most independent, respectable, and generally informed persons among the proprietors. The committee of management will then proceed to elect a chairman and subordinate officers; to fix upon their place of meeting, and to arrange the order of their business. 3542. Aresident engineer and land-surveyor and valuer should now be fixed on, and probably also a local or select committee: auditors of accounts will be appointed, and salaries determined. The chief engineer will now revise the line, and divide it into different parts, assigning names to each for convenient reference. Of these distinct parts, or divisions, a separate account of the expenses should be strictly kept by the resident engineer, the overseers, or counters, as they are generally called, that the engineer is to recommend or employ upon the works, and by the office clerks in a ledger, with proper heads for each length of canal, set of locks, tunnel, embankment, deep-cutting, reservoir, aqueduct, or other great work, that may form a separate division: such particular and divided accounts of the works will prove of the most essential service to the committee, and to all others concerned, in informing and maturing their judgment on the actual or probable expense of every different kind of work; and will enable the committee to account to the proprietors how great, and sometimes unavoidable, as well as unexpected, expenses may be incurred. 3543. Such lands as are wanted should now be treated for by the land-surveyor, and the purchase and conveyance concluded with the approbation of the committee, and the aid of the solicitor, with or without the aid of the sheriff and a jury, as the case may require. In general, the ground for reservoirs and locks ought to be the first purchased, to permit the embankments and masonry to be proceeded with. SECT. IV. Of the Execution of the Works. 3544. The first operation of execution is the setting out of the work by the resident engineer and surveyor. He will trace and mark the levels accurately of each pound or level reach of the canal, marking them with stakes, and comparing his work with the bench marks, and making two or more of the men who assist him perfectly acquainted with their situations, in case they should be deranged by cattle or otherwise 3545. The calculations for excavation is the next part of execution. The great desideratum in canal-digging is, that the stuff that is dug from one part of the work shall, with the least labor or distance of moving, exactly supply or form the banks that are to be raised in another, so that, on the completion of the work, no spoil banks, or banks of useless soil, shall remain, or any ground be unnecessarily rendered useless by excavations or pits. Six different cases will be found frequently to occur in the cutting or forming a canal. In each case the towing-bank (fig. 449 a.), is wider than the offbank (b); and in all, the sides slope one and half feet for one foot in depth, that being found the least slope which can be given. 3546. Where there is deep cutting on one side (c), or both (d, e), a bench or berm (c, e) خنة 449 is provided to retain and prevent the loose earth that may moulder down from the upper bank from falling into the canal. The banks are usually made one foot higher than the water is intended to stand in them. 3547. In level cutting (fig. 449 a, b), the height of the canal should be so contrived, that in any cross section the sum of the areas of the made banks (a, b) should just equal that of the area of the section of excavation (i). 3548. In side-lying ground (fig. 449 c, and fig. 450 f), the same object may be attained with a little extra calculation; and in all other cases (g, h), the engineer will shew the J 450 h perfection of his skill in so conducting the line, that every embankment shall have deep cutting at both, or at least at one of its ends, to furnish the extra stuff with least expense in moving it; in like manner, every deep cutting (d, e) should have embankments at one or both of its ends, to receive the extra stuff. 3549. Before cutting out the lock-spit, or small trench between the several slope holes, as a guide to the men who are to dig, the engineer ought to cause holes to be dug in the line of the canal, near every second or third level peg, or oftener, if the soil be variable, in order to prove the soil to a greater depth, by two or three feet, than the cutting of the canal is to extend; and each of these the engineer ought carefully to inspect, in order to determine what puddling or lining will be necessary; and what will be the difficulties of digging, owing to the hardness of the stuff, or to water that must be pumped out, &c. ; all which circumstances, as well as the extra distance that any part of the stuff may require to be moved, must be well considered before the work can be let to the contractors. 3550. The puddling or lining of a canal, to make it hold water, is a matter of the greatest importance, and we shall consider five cases that are likely to occur or present themselves in the search into the soil that is to be dug, by sinking holes as abovementioned. The first case we suppose to be that in which the whole is clay, loam, or other water-tight stuff; all soils that will hold water, and not let it soak or percolate freely through them, are called water-tight. Our second case is that in which the whole cutting will be in sand, gravel, loose or open rock, or any other matters that will let water easily through them, and such are called porous soils or stuffs. The third case, we suppose to have a thin stratum of water-tight stuff on the surface, and to have porous stuff for a considerable depth below. The fourth case may have porous stuff near the surface, and water-tight stuff' at the bottom of the canal. The fifth case is that where water-tight stuff appears on the surface; and below this a stratum of porous stuff, but having again water-tight stuff at no great distance below the intended bottom of the canal. The new raised banks are always to be considered as porous stuff, as, indeed, they will always prove at first, and in a great portion of soils they would ever remain so, unless either puddling or lining was applied; all ground that has been dug or disturbed, must also be considered as porous. It should also be remarked, that any kind of soil which is perforated much by worms or other insects, should, in canal digging, be considered as porous stuff. |