248

HISTORY OF ENGINEERING.

Book I.

17 feet; they prevent the lower gates of the lock from opening in the usual way> and areconsequently worked by hooks.

The construction of the bridges is the same as that of the locks, the facings of the wallsbeing of freestone, and the rest moellon rusticated ; there are several skew bridges ; thosefor uniting the lands of individuals are for the most part constructed of timber, and arcformed over the lock gates; they are composed of three beams, sustained by struts, restingon the gate post, and by a wheel on the side walls; the roadway is 9 feet wide, andformed by planking.

Mouths of the Canal in the Loire and the Saone . — The bed of the Loire being subject tochange, the current tends to run from the right bank on which is the lock, and themargins become silted up ; to avoid this a stone dyke is constructed on the opposite sideof a curvilinear form, for the purpose of directing the current to the mouth of the canal,which is up the stream, and forms an acute angle with the bank ; this does not quite answerthe purposes intended, and cleaning the entrance of the canal cost annually from 3000to 4000 francs ; in 1811 a cotter-dam was formed in front, which is too high, and tends toproduce an undermining at the foot of the opposite banks; this has been prevented bythrowing in stones ; since the termination of this work, the cleansing costs annually only300 or 400 francs.

The Mouth o f the Saone ; the direction of the canal forms a right angle with the bank ofthe river, and the guard lock, instead of being placed on the bank, is 200 metres distantfrom it; this interval is constantly dragged to allow a passage for the boats.

This canal unites the Loire to the Saone ; from Dijon to the summit level there arethirty locks, rising about 240 feet in G300 metres ; and the length of the summit level isabout 3940 metres; the descent to the Saone is by fifty locks, or 400 feet, in a distance of4700 metres.

The whole length of the canal is 114,322 metres, the length of each lock 100 feet, andbreadth 16 feet; the breadth of the canal at top 48 feet, at bottom 30 feet, and the averagedepth 5 feet 3 inches.

Canal of Languedoc was executed in the reign of Louis XIV. from designs furnished byFrancis Andreossy, an Italian engineer, by whom locks were introduced into France , pro-ducing a new epoch in the history of canals, and without which inland navigation nevercould have been brought to its present state of perfection.

The canal of Languedoc crosses the isthmus which connects Spain with France , and passesthrough the valley between the Pyrenees and the river Rhone ; and it appears that acontract for its completion was made with Paul Riquet on the 14th of October, 1666.

This canal is united with the Garonne below Toulouse , and by means of eight lockspasses round the western side of the city, then along the south side of the river Lers,and by thirteen locks it ascends to Villefranche , rising another five locks. From theGaronne to the summit, a distance of nearly 24 miles, it rises by twenty-six locks, a heightof 207 feet; the length of the summit level is 3| miles, after which the canal descends toCastelnaudary , an ancient town occupying the site of Sostomagus, where the great basin isconstructed ; it soon after falls into the Aude near Carcassonne , having crossed several smallstreams, and descends by thirty-seven locks. It then traverses the northern side of theAude and the town of Treves, to the long level near the Olonzac ; in this latter course it passesover several streams, and descends by twenty-two locks. Near Olanzac commences thelong level, and where it crosses the Cesse, the canal of Narbonne branches off; the canal ofLanguedoc passes to the north of Capestang by several windings around Mount Ecurene,and then by a tunnel of 281 yards, under a ridge of mountain called Malpas ; eight locksafterwards ascend to Fonseranne; the level is then 17 miles in length. After passing theselocks it crosses the Orb, near the south side of Bezieres , then the rivers Libron andHerault , and north of Agde winds round to the Lake Bagnes, enters the Lake Thau,and passes through to Cette , on the coast of the Mediterranean ; there are five locksduring the latter part of its course. The distance from the summit of Naurouse to Cettethe port, is 12l£ miles, and the fall 621 feet 6 inches.

The length of the canal altogether is 148 miles, and the lake Thau 9^ miles, whichbeing very shallow at the western end, the canal is carried through it for a considerabledistance by means of artificial dykes.

This canal cost 14,000,000 livres; the king defrayed one-half, and the province ofLanguedoc the other. There being some difficulty in making an arrangement with theproprietors of the lands through which it passed, in 1666, the king issued an edict, whichstates “that Paul Riquet , the undertaker of this work, should take all lands and heredita-ments necessary for the construction of the canal, together with all streams, warehouses,banks, roadways, locks, &c. &c.” which were to be paid for, after a valuation made by com-petent persons, named by commissaries appointed by the king. The design was fur-nished by M. Clerville, the most eminent engineer in France , who had also the direction ofthe work ; the first stone was laid on the 29th July, 1666, at Cette , and in May, 1681, thecommunication between the two seas was complete, after fifteen years* labour, Hie canal