Having thus stated the commencement of the Ca nal, we shall next give a general description or outline of the country through which it passes, proceeding from the east to the west sea. Mr Watt, in his Re port of 1773, observes, that the regularity of this ex tensive tract is quite astonishing, in so mountainous and rugged a country. • Mr Jessop, in his first Re port, says, .that at some early age of the world, it seems probable this immense chasm (the line of the Canal) has been nearly open from sea to sea. Though the investigations of the Geologist have, as yet, we may observe, made small progress in elucidating the probable revolutions which the earth has undergone; and although, upon every band, he is met by difficul tics, and contradictory appearances, yet it is scarce ly possible that any one who has examined and considered the appearances of this interesting chain of salt and fresh water lochs or lakes, can doubt that, at some period of the world, the sea has occu pied a higher level ; that the country in the vici nity of the towns of Inverness and Fort-William have been, at one time, covered by it to a much greater extent ; and that at some period the whole of this chain of lakes, thus forming one great sheet of water, had only one barrier, at the eastern, and another at the western extremity. These barriers or fences, in the course of time, being worn down, the increased issue of the waters from the ori. ginal loch, would have a tendency to lower the surface of the water, and thereby expose the highest parts pf the bed, !and thus ultimately form the divisions or necks of land which we now find separating and dividing these lochs. So much of probability doe, this theory carry with it, that, along the whole length of the line of canal, the excavated matters, with little exception, are found to consist chiefly of gravel and water-worn stones : these subdivisions, once formed and exposed to the atmosphere, would acquire vege table and adventitious matters ; and in time, by the wearing of the beds of the original outlets, these patches of land would rapidly increase.' • But whatever may have been the actual state of mat ters here, at an early period, the great vale, or per haps more properly, the chasm, of the Ness and Lochy, is, without exception, the most remarkable in the king for, in a distance of about sixty miles, from sea to sea, the summit level of this navigation is only about 94 feet above the level of the ocean. There are, in deed, some approximations to this state of things; as, for example, between Crinan and Lochgilphead,— (the line of the Crinan Canal.) This may also be DO. ticed of various other parts of the kingdom,—as be tween the great Wash of Lincoln on the east, and the vale of Gloucester and Severn on the west ; be. tween the river Tyne and the Solway Firth ; the Firth of Forth, by Blair Drummond Moss, and the Clyde. • Perhaps the nearest to the vale of the Ness and Lochy of those mentioned, is that between the Forth and the Clyde, which passes between two ranges of hills ; but all of these come far short, in sublimity of effect, to the line of the Caledonian Canal, where the hills rise to a stupendous height, while the bot• tom of the dell, or vale, is interspersed with exten sive sheets of water.
We shall now proceed to notice the position of the first, or sea lock, of the canal at Loch Beau '', on the east, and so advancing Westward, de. scribe the works of this great Inland Navigation. The precise spot originally intended for the East ern Sea or tide-lock, was rather to the north-east ward of the present site ; but the ground, upon trial, was found not to answer the purposes of a foun dation, for such a weight of masonry. The sea lock Of Clachnaharry is about three quarters of a mile to the westward of the much frequented Ferry of Kessock. It extends upwards of 400 yards into the sea, or beyond the high water mark, where it is ex pected a depth of water, equal to about 30 feet, will be obtained at high water of spring-tides. The writer of this article, attracted by the inagnitudo and novelty of this particular operation, visited it in the autumn of 1811, when the masonry was then in a half finished state ; and cannot pass this ex tensive and interesting part of the works, without noticing more particularly its progress and comple tion. The unexampled price of foreign timber, es
pecially of large dimensions, about the year 1807, had induced the Engineers to delay commencing the sea lock as long as possible, in hopes of a change of circumstances. In 1808, however, it was thought advisable to lay down an imniense quan tity of rubbish, in the form of two parallel mounds, extending from the second canal lock into Beau ly Firth. This was done by means of two sets of railways ; one from the ruble stone quarry of' Clachnaharry ; and the other, consisting of a kind of indurated clay, was carried across the line of the ca nal from an adjacent hill, along the site of the intend gl sea lock; that it might answer the purposes of a coffer-clans, and consolidate the subsoil or strata of matters deposited from the joint operation of the River and Firth of Beauly. These strata, when bored to the depth of about 54 feet, were found to consist of soft bluish clay or mud, overlying a whitish clay, similar to the base of the neigh.
bouring hill of Clachnaharry. These mounds of rubbish extending into the sea, were found to settle and subside so much, as to require an additional stratum of 11 feet in thickness to restore them to their former level ; an effect which was, no doubt, expected ; but this, however, was the means of sug gesting the propriety of laying also a quantity of rubbish between these mounds or parallel banks upon the site of the sea lock, which, in the same manner, bad the effect of compressing the subsoil, and pre paring it for the immense weight of masonry it had to support, which could not have been the case, had it been built with a coffer-dam in the usual way : the finished work might, in that case, have subsided in the same manner as the mounds had done, which would have been productive of the most serious con sequences to the work. This consideration, in con junction with the high price of timber, induced Messrs Jessop and Telford to adopt the simple but more secure method just described ; and when the mass of rubbish had sufficiently subsided, they com menced their operations by excavating the lock-pit in the mound of rubbish lying upon the site of the lock to the depth of about 30 feet, when the sub soil was found in such a state of consolidation, that the excavation had proceeded to a consider able depth before it was found necessary to have re course to the power of steam, for pumping the wa ter out of the lock-pit. It has indeed been remark ed of the adhesive nature of this ground, that al though piles were driven with great ease into it, yet, after they had remained for a time in silt, it was neither found practicable to draw them out, nor to drive them farther into the ground. When the area of the lock-pit had been dug to a sufficient depth, a course of large stones, two feet in thickness, was laid in the middle for supporting the key-stone of the in verted arch of the lock. This foundation course in creased in thickness to five feet towards the spring ing in front of the side walls, which were built upon it with all possible dispatch, in lengths or compart ments of six yards at a time, till the whole was brought to the height of the silt, or to about eight feet, that it might not be undulyexposed to wet and dry. In this manner the work proceeded, till the chamber of the lock was formed by the side walls, when the inverted arch and sides of squared masonry was built upon this layer of ruble work, which finial ed the work. The construction of this lock is par ticularly noticed in the Parliamentary Reports with marks of approbation to all concerned ; and, with much propriety, the Commissioners have there been pleased to notice the successful exertions of Mr Da vidson, the Resident Engineer.