CANAL

, in general, denotes a long, round, hollow instrument, through which a fluid matter may be conveyed. In which sense, it amounts to the same as what is otherwise called a pipe, tube, channel, &c. Thus the Canal of an aqueduct, is the part through which the water passes; which, in the ancient works of this kind, is lined with a coat of mastic of a peculiar composition.

Canal more particularly denotes a kind of artificial river, often furnished with locks and sluices, and sustained by banks or mounds. They are contrived for divers purposes; some for forming a communication between one place and another; as the Canals between Bruges and Ghent, or between Brussels and Antwerp: Others for the decoration of a garden, or house of pleasure; as the Canals of Versailles, Fontainbleau, St. James's Park, &c: And others are made for draining wet and marshy lands; which last however are more properly called water-gangs, drains, ditches, &c.

It is needless to enumerate the many advantages arising from Canals and artificial navigations. Their utility is now so apparent, that most nations in Europe give the highest encouragement to undertakings of this kind wherever they are practicable. Nor did their advantages escape the observation of the Ancients. From the earliest accounts of society we read of attempts to cut through large isthmuses, to make communications by water, either between one sea and another, or between different nations, or distant parts of the same nation, where land-carriage was long and expensive.

Egypt is full of Canals, dug to receive and distribute the waters of the Nile, at the time of its inundation. They are dry the rest of the year, except the Canal of Joseph, and four or five others, which may be ranked as considerable rivers. There were also subterraneous Canals, or tunnels, dug by an ancient king of Egypt, by which those lakes, formed by the inundations of the Nile, were conveyed into the Mediterranean sea.

Herodotus relates, that the Cnidians, a people of Coria, in Asia Minor, designed to cut through the isthmus which joins that peninsula to the continent; but were superstitious enough to give up the undertaking, because it was interdicted by an oracle.

Several kings of Egypt attempted to join the RedSea to the Mediterranean; a project which Cleopatra was very fond of. This Canal was begun, according to Herodotus, by Necus son of Psammeticus, who desisted from the attempt on an answer from the oracle, after having lost 120 thousand men in the enterprise. It was resumed and completed by Darius son of Hystaspes, or, according to Diodorus and Strabo, by Ptolomy Philadelphus; who relate that Darius relinquished the work on a representation made to him by unskilful engineers, that the Red-Sea, being higher than the land of Egypt, would overflow and drown the whole country. It was wide enough for two galleys to pass abreast, and its length was four days sailing. Diodorus adds, that it was also called Ptolomy's river; that this prince built a city at its mouth on the Red-Sea, which he called Arsinoë, from the name of his favourite sister; and that the Canal might be either opened or shut, as occasion required. Diod. Sic. lib. 1; Strabo, Geog. lib. 17; Herod. lib. 2. Soliman the 2d, emperor of the Turks, employed 50 thousand men in this great work; which was completed under the caliphate of Omar, about the year 635; but was afterward allowed to fall into neglect and disrepair; so that it is now difficult to discover any traces of it. Hist. Acad. Scienc. ann. 1703, pa. 110.

Both the Greeks and Romans intended to make a Canal across the Isthmus of Corinth, which joins the Morea and Achaia, for a navigable passage by the Ionian sea into the Archipelago. Demetrius, Julius Cæsar, Caligula, and Nero, made several unsuccessful efforts to open this passage. But as the Ancients were entirely ignorant of the use of water-locks, their whole | attention was employed in making level cuts, which is probably the chief reason why they so often failed in their attempts. Charlemagne formed a design of joining the Rhine and the Danube, to make a communication between the Ocean and the Black-Sea, by a Canal from the river Almutz which discharges itself into the Danube, to the Reditz, which falls into the Maine, which last falls into the Rhine near Mayence or Mentz: for this purpose he employed a prodigious number of workmen; but he met with so many obstacles from different quarters, that he was obliged to give up the attempt.

A new Canal for conveying the waters of the Nile from Ethiopia into the Red-Sea without passing into Egypt, was projected by Albuquerque, viceroy of India for the Portuguese, to render Egypt barren and unprofitable to the Turks.—M. Gaildereau attributes the frequency of the plague in Egypt, of late days, to the decay, or stopping up of these Canals; which happened upon the Turks becoming masters of the country.

In China, there is scarce a town or village without the advantage either of an arm of the sea, a navigable river, or a Canal, by which means navigation is rendered so common, that there are almost as many people on the water as the land. The great Canal of China, is one of the wonders of art, extending from north to south quite across the empire, from Pekin to Canton, a distance of 825 miles, and was made upwards of 800 years ago. Its breadth and depth are sufficient to carry barks of considerable burden, which are managed by sails and masts, as well as towed by hand. On this Canal it seems the emperor employs near ten thousand ships. It passes through, or by, 41 large cities; there are in it 75 vast locks and sluices, to keep up the water, and pass the ships where the ground will not admit of sufficient depth of channel, beside several thousand draw and other bridges. Indeed, F. Magaillane assures us, there are passages from one end of China to the other, the space of 600 French leagues, either by Canals or rivers, except a single day's journey by land, necessary to cross a mountain.

The French at present have many fine Canals. That of Briere, otherwise called the Canal of Burgundy, was begun under Henry IV, and finished under the direction of cardinal Richelieu in the reign of Louis XIII. This Canal makes a communication between the Loire and the Seine, and so to Paris. It extends 11 French great leagues from Briere to Montargis, and has 42 locks upon it.

The Canal of Orleans was begun in 1675, for establishing a communication also between the Seine and the Loire. It is considerably shorter than that of Briere, and has only 20 sluices.

The Canal of Bourbon was but lately undertaken: its design is to make a communication from the river Oise to Paris.

But the greatest and most useful work of this kind, is the junction of the Ocean with the Mediterranean by the Canal of Languedoc, called also the Canal of the two seas. It was proposed in the reigns of Francis I and Henry IV, and was begun and finished under Louis XIV; having been planned by Francis Riquet in the year 1666, and finished before his death, which happened in 1680. It begins with a large reservoir 4000 paces in circumference, and 24 feet deep, which receives many springs from the mountain Noire. The Canal is about 200 miles in length, extending from Narbonne to Tholouse, being supplied by a number of rivulets in the way, and furnished with 104 locks or sluices, of about 8 feet rise each. In some places it is carried over bridges and aqueducts of vast height, which give passage underneath to other rivers; and in some places it is cut through solid rocks for a mile together.

The new Canal of the lake Ladoga, cut from Volhowa to the Neva, by which a communication is made between the Baltic, or rather Ocean, and the Caspian sea, was begun by the czar Peter the 1st in 1719: by means of which the English and Dutch merchandize is easily conveyed into Persia, without being obliged to double the Cape of Good Hope.—There was a former Canal of communication between the Ladoga lake and the river Wolga, by which timber and other goods had been brought from Persia to Petersburg; but the navigation of it was so dangerous, that a new one was undertaken.

The Spaniards have several times had in view the digging a Canal through the Isthmus of Darien, between North and South America, from Panama to Nombre de Dios, to make a ready communication between the Atlantic and the South Sea, and thus afford a straight passage to China and the East Indies.

In the Dutch, Austrian, and French Netherlands, there is a great number of Canals: that from Bruges to Ostend carries vessels of 200 tons. But it would be an endless task to describe the numberless Canals in Holland, Germany, Russia, &c. We may therefore only take a view of those in our own country.

In England, that ancient Canal from the river Nyne, a little below Peterborough, to the river Witham, three miles below Lincoln; called by the modern inhabitants Caerdike; may be ranked among the monuments of the Roman grandeur, though it is now most of it filled up. Morton will have it made under the emperor Domitian. Urns and medals have been discovered on the banks of this Canal, which seem to confirm that opinion. Yet some authors take it to be a Danish work. It was 40 miles in length; and, so far as appears from the ruins, must have been very broad and deep. Notwithstanding that early beginning, it is not long since Canals have been revived in this country. They are now however become very numerous, particularly in the counties of York, Lincoln, and Cheshire. Most of the counties between the mouth of the Thames and the Bristol channel are connected together either by natural or artificial navigations; those upon the Thames and Isis reaching within about 20 miles of those upon the Severn.

The Canal for supplying London with water by means of the New River, was projected and begun by Mr. Edward Wright, author of the celebrated treatise on Navigation, about the year 1608; but finished by Mr. (afterwards Sir Hugh) Middleton, five years after. This Canal commences near Ware, in Hertfordshire, and takes a course of 60 miles before it reaches the cistern at Islington, which supplies the several water pipes that convey it to the city and parts adjacent. In some | places it is 30 feet deep, and in others it is conveyed over a valley between two hills, by means of a trough supported on wooden arches, and rising above 23 feet in height.

The Duke of Bridgwater's Canal, projected and executed under the direction of Mr. Brindley, was begun about the year 1759. It was first designed only for conveying coals to Manchester, from a mine in the duke's estate; but has since been applied to many other useful purposes of inland navigation. This Canal begins at a place called Worsley-mill, about 7 miles from Manchester, where a bason is made capable of holding all the boats, and a great body of water which serves as a reservoir or head to the navigation. The Canal runs through a hill by a subterraneous passage, large enough for admitting long flat-bottomed boats, which are towed by a rail on each hand, near three quarters of a mile, to the coal-works. There the passage divides into two channels, one of which goes off 300 yards to the right, and the other as many to the left; and both may be continued at pleasure. The passage is in some places cut through the solid rock, and in others arched over with brick; and air-funnels, some of which are near 37 yards perpendicular, are cut, at certain distances, through the rock to the top of the hill. The arch at its entrance is about 6 feet wide, and about 5 feet high from the surface of the water; but widens within, so that in some places the boats may pass one another, and at the pits it is 10 feet wide. When the boats are loaded and brought out of the bason, five or six of them are linked together, and drawn along the Canal by a single horse, and thus reaching Manchester in a course of nine miles. It is broad enough for two barges to pass or go abreast; and on one side there is a good road for the passage of the people, and the horses or mules employed in the work. The Canal is raised over public roads by means of arches; and it passes over the navigable river Irwell near 50 feet above it; so that large vessels in full sail pass under the Canal, while the duke's barges are at the same time passing over them. This Canal joins that which passes from the river Mersey towards the Trent, taking in the whole a course of 34 miles.

The Lancaster Canal begins near Kendal, and terminates near Eccleston, comprehending the distance of 72 1/2 miles.

The Canal from Liverpool to Leeds is 108 1/3 miles: that from Leeds to Selby, 23 1/4 miles; from Chichester to Middlewich, 26 3/4 miles; from the Trent to the Mersey, 88 miles; from the Trent to the Severn, 46 1/2 miles. The Birmingham Canal joins this near Wolverhampton, and is 24 1/4 miles: the Droitwich Canal is 5 1/2 miles: the Covehtry Canal, commencing near Lichfield, and joining that of the Trent, is 36 1/4 miles: the Oxford Canal breaks off from this, and is 82 miles: the Chesterfield Canal joins the Trent near Gainsborough, and is 44 miles.

A communication is now formed, by means of this inland navigation, between Kendal and London, by way of Oxford; between Liverpool and Hull, by the way of Leeds; and between the Bristol channel and the Humber, by the junction formed between the Trent and the Severn. Other schemes have been projected, which the present spirit of improvement will probably soon carry into execution, of opening a communication between the German and Irish seas, <*> reduce a <*> zardous navigation of more than 800 miles by sea, into a little more than 150 miles by land, or inland navigation; and also of joining the Isis with the Severn.

In Scotland, a navigable Canal between the Forth and Clyde, which divides that country into two parts, was thought of more than a century since, for transports and small ships of war. It was again projected in the year 1722, and a survey made; but nothing more was done till 1761, when the then lord Napier, at his own expence, had a survey, plan, and estimate made on a small scale. In 1764, the trustees for fisheries, &c, in Scotland, procured another survey, plan, and estimate of a Canal 5 feet deep, which was to cost 79,000 pounds. In 1766, a subscription was obtained by a number of the most respectable merchants in Glasgow, for making a Canal 4 feet deep and 24 feet in breadth; but when the bill was nearly obtained in parliament, it was given up on account of the smallness of the scale, and a new subscription set on foot for a Canal 7 feet deep, estimated at 150,000 pounds. This obtained the sanction of parliament; and the work was begun in 1768, by Mr. Smeaton the engineer. The extreme length of the Canal from the Forth to the Clyde is 35 miles, beginning at the mouth of the Carron, and ending at Dalmure Burnfoot on the Clyde, 6 miles below Glasgow, rising and falling 160 feet by means of 39 locks, 20 on the east side of the summit, and 19 on the west, as the tide does not ebb so low in the Clyde as in the Forth by 9 feet; and it was deepened to upwards of 8 feet. This Canal was finished a few years since, after having experienced some interruptions and delays, for want of resources, and is esteemed the greatest work of the kind in this island. Vessels drawing 8 feet water, with 19 feet in the beam and 73 feet in length, pass with ease; and the whole enterprise displays the art of man in a high degree. To supply the Canal with water was of itself a very great work. There is one reservoir of 50 acres 24 feet deep, and another of 70 acres 22 feet deep, in which many rivers and springs terminate, which it is expected will afford sufficient supply of water at all times.

The Practice of Canal Digging and Inland Navigations.

The particular operations necessary for making artificial navigations, depend upon a number of circumstances. The situation of the ground; the vicinity or connection with rivers; the ease or difficulty with which a proper quantity of water can be obtained: these and many other circumstances necessarily produce great variety in the structure of artificial navigations, and augment or diminish the labour and expence of executing them. When the ground is naturally level, and unconnected with rivers, the execution is easy, and the navigation is not liable to be disturbed by floods: but when the ground rises and falls, and cannot be reduced to a level, artificial methods of raising and lowering vessels must be employed; which likewise vary according to circumstances.

Sometimes a kind of temporary sluices are employed, to raise boats over falls or shoals in rivers, by a very simple operation. Two pillars of mason-work, with grooves, are fixed, one on each bank of the river, at | some distance below the shoal. The boat having passed these pillars, strong planks are let down across the river by pulleys into the grooves; by which means the water is dammed up to a proper height for allowing the boat to pass up the river over the shoal.

The Dutch and Flemings at this day sometimes, when obstructed by cascades, form an inclined plane or rolling-bridge upon dry land, along which their vessels are drawn from the river below the cascade, into the river above it. This it is said was the only method employed by the Ancients, and still sometimes used by the Chinese. These rolling-bridges consist of a number of cylindrical rollers which turn easily on pivots. And a mill is commonly built near; so that the same machinery may serve the double purpose of working the mill and drawing up vessels.

But in the present improved state of inland navigation, these falls and shoals are commonly surmounted by means of what are called locks or sluices. A lock is a bason placed lengthwise in a river or Canal, lined with walls of masonry on each side, and terminated by two gates placed across the Canal, where there is a cascade or natural fall of the country; and so construct. ed, that the bason being filled with water by an upper sluice to the level of the waters above, a vessel may ascend through the upper gate; or the water in the lock being reduced to the level of the water at the bottom of the cascade, the vessel may descend through the lower gate: for when the waters are brought to a level on either side, the gate on that side may be easily opened.

But as the lower gate is strained in proportion to the depth of water it supports, when the perpendicular height of the water exceeds 12 or 13 feet, it becomes necessary to have more locks than one. Thus, if the fall be 16 feet, two locks are required, each of 8 feet fall; and if the fall be 25 feet, three locks are necessary, each having 8 feet 4 inches fall.—It is evident that the sidewalls of locks should be made very strong: and where the natural foundation is bad, they should be founded on piles and platforms of wood. They should likewise slope outwards, in order to resist the pressure of the earth from behind.

To illustrate this by representations: Plate 37, fig. 1, is a perspective view of part of a Canal, with several locks &c; the vessel L being within the lock AC.— Fig. 2 is an elevation or upright section along the Canal; the vessel L about to enter.—Fig. 3, a like section of a lock full of water; the vessel L being raised to a level with the water in the superior Canal.—And fig. 4 is the plan or ground section of a lock: where L is a vessel in the inferior Canal; C, the under gate; A, the upper gate; GH, a subterraneous passage for letting water from the superior Canal run into the lock; and KF, a subterraneous passage for water from the lock to the inferior Canal.

X and Y (fig. 1) are the two flood-gates, each of which consists of two leaves, resting upon one another, so as to form an obtuse angle, the better to resist the pressure of the water. The first (X) prevents the water of the superior Canal from falling into the lock; and the second (Y) dams up and sustains the water in the lock. These flood-gates ought to be very strong, and to turn freely upon their hinges. They should also be made very tight and close, that as little water as possible may be lost. And, to make them open and shut with ease, each leaf is furnished with a long lever Ab, Ab; Cb, Cb.

By the subterraneous passage GH (fig. 2, 3, 4) which descends obliquely, by opening the sluice G, the water is let down from the superior Canal D into the lock, where it is stopped and retained by the gate C when shut, till the water in the lock comes to be on a level with the water in the superior Canal D; as represented in fig. 3. When, on the other hand, the water contained by the lock is to be let out, the passage GH must be shut, by letting down the sluice G; the gate A must also be shut, and the passage KF opened by raising the sluice K. A free passage being thus given to the water, it descends through KF, into the inferior Canal, until the water in the lock be on a level with the water in the inferior Canal B; as represented in fig. 2.

Now suppose it be required to raise the vessel L (fig. 2) from the inferior Canal B to the superior one D. If the lock be full of water, the sluice G must be shut, as also the gate A, and the sluice K opened, so that the water in the lock may run out till it become to a level with the water in the inferior Canal B. When the water in the lock comes to be on a level with the water at B, the leaves of the gate C are opened by the levers Cb, which is easily performed, the water on each side of the gate being in equilibrio; the vessel then sails into the lock. After this, the gate C and the sluice K are shut, and the sluice G opened, in order to fill the lock, till the water in the lock, and consequently the vessel, be upon a level with the water in the superior Canal D; as is represented in fig. 3. The gate A is then opened, and the vessel passes into the Canal D.

Again let it be required to make a vessel descend from the Canal D into the inferior Canal B. If the lock be empty, as in fig. 2, the gate C and sluice K must be shut, and the upper sluice G opened, so that the water in the lock may rise to a level with the water in the upper Canal D. Then, opening the gate A, the vessel will pass through into the lock. This done, shut the gate A and the sluice G; then open the sluice K, till the water in the lock be on a level with the water in the inferior Canal; this done, the gate C is opened, and the vessel passes along into the Canal B, as was required.

CATENARY. Line 4, for ACB read BAC.— 1. 6, for A and B read C and B. After which add, It is otherwise called the Elastic Curve.

CHALDRON. Line 4, for 2000 pounds, read 28 cwt. or 3136 pounds. At the end add, By act of parliament, a Newcastle Chaldron is to weigh 52 1/2 cwt, or 3 waggons of 17 1/2 cwt, or 6 carts of 8 3/4 cwt each, making 52 1/2 cwt to the Chaldron. The statute London Cha<*>n is to consist of 36 bushels heaped up, each bushel to contain a Winchester bushel and one quart, and to be 19 1/2 inches diameter externally. Now it has been found by repeated trials, that 15 London Chaldrons are equal to 8 Newcastle Chaldrons, which, reckoning 52 1/2 cwt to the latter, gives 28 cwt to the former, or 3136 lbs to the London Chaldron.

This I find nearly confirmed by experiment. I | weighed one peck of coals, which amounted to 21 3/4 lb. Then 4 times this gives 87 lb for the weight of the bushel; and 36 times the bushel gives 3132 lb for the Chaldron; to which if the weight of the odd quart be added, or 3 lb nearly, it gives 3135 lb for the weight of the Chaldron, which is only one pound less than by statute.

Pa. 287, col. 2, l. 20, for YX - a - x, read YX = a - x.

CIRCLE of Curvature. To what is said of this article in the Dictionary, may be added what follows.

A circular are is the only curve line that is equally curved in every point. In all other curve lines, such as the are of an ellipse, or a parabola, or an hyperbola, or a cycloid, the curvature is different in different points, and the degree of curvature in any point is estimated by the curvature of a Circle which is said to have the same curvature as the proposed curve line in that point; by which is understood the Circle which, having the tangent of the proposed curve in the said point for its tangent, approaches so nearly to the proposed curve that no other Circle whatever can be drawn between it and that curve.

This Circle is also said to osculate the curve in the said point, and is therefore often called the osculating Circle, as well as the Circle of equal curvature with the curve in the said point. And the radius of this Circle is called the radius of curvature of the proposed curve in the said point; also its centre is called the centre of curvature.

Now there are some curve lines so very highly curved in some particular points, that every Circle, of how small a radius soever, having the tangent to the curve in one of those points for its tangent, will pass without the curve, or between the curve and its tangent. This, for example, is the case with the curve of a cycloid in the two points contiguous to its base, as also with the cissoid at its vertex. And in such points the curvature of these curves is said to be infinite, because it is greater than the curvature of any Circle, how small soever. Also the radius of the Circle of curvature in such points is nothing; the length of that radius being always inversely or reciprocally as the degree of curvature at any point.

The theory of these Circles of equal curvature with curves in particular points was first cultivated by Apollonius in his Conic Sections: and it has since been carried much farther by several great mathematicians of modern times; particularly by Mr. Huygens in his doctrine of Evolute Curves and Curves of Evolution, and by the great Sir Isaac Newton. See Curvature.

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ABCDEFGHKLMNOPQRSTWXYZABCEGLMN

Entry taken from A Mathematical and Philosophical Dictionary, by Charles Hutton, 1796.

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* CANAL
CLARKE (Dr. Samuel)
CLEF