One of the most difficult operations in forming this navigation, is the deepening of Loch Dough four. This Loch, as will be observed from the map, is connected with the eastern end' of Loch Nest by the sallow pass of Bona Ferry. It is about one mile in length, and varies from 100 to 150 fathoms in breadth. From the rapid current at Bona Ferry, it appears that the fall of the water, towards the river and the sea, commences here, and with Loch Doughfour forms a receptacle for much of the gravel and debris, which is brought down from the exten sive shores of Loch Ness. This part of the naviga tion it was therefore found necessary to deepen, by artificial means, in some places, to nearly the full depth of the canal. This was done partly by a powerful dredging-machine, which is floated upon a barge. The apparatus is somewhat complicated, but the chief part is a succession of iron buck ets, connected by an endless chain made to re volve round a frame, which is let down into the water to any convenient depth, and lifts silt, gravel, and other matters from the bottom. This machine has been long in use in clearing mud from the bot tom of harbours and rivers. Till of late years it was worked by the power of men and horses, but where much is to be done, as on the Caledonian Canal, the steam-engine is substituted m the moving power ; which requires a barge or vessel of great too carry it. The dredging-machine has been used with much success at Loch Doughfour, where it is calcu lated to have lifted about 90,000 tons of gravel in a twelvemonth. The stuff lifted is received from the dredging-machine, as it comes out of the water, in punts or lighters, and is carried to a proper place for deposition. By such mewls, the navigation from the eastern end of Loch Doughfour to Loth Ness is brought to a depth no where less than ten feat. In the course of this arduous operation, the roots of large trees have been lifted, weighing several tons. Even rock has been excavated at this 'depth under water, by means of placing picks instead of buckets upon the revolving apparatus.
To obtain the additional depth of water, beyond the reach of the dredging-machine, a weir or dam is to be placed across the eastern end of Loch Doughfour, where the river Ness properly com mences. This dam or weir will not only deepen the loch, but will check the current at Bona Ferry, aid prevent the tendency of the debris from being carried from Loch Ness into Loch Doughfour. The waters of the Ness will then be drawn off from the surface of the loch, and will cease to carry with it quantities of stones and gravel, as, at present, and Loch Dough four will become an excellent place of anchorage for wind-bound ships. The operation of building this dam or weir across the Ness, has not yet been cow mowed. It will be attended with considerable difficulty from the current of the river, and from the requisite strength and important purposes to be served by it.
Loch Ness, forming so considerable a part of this navigation, is about twenty-two miles in length, of a pretty uniform breadth, varying from about one mile to three quarters of a mile. Its depth of wa• ter is from 106 to 180 fathoms in the middle or deepest parts. The aides of the loch appear to be steep and precipitous, as it suddenly deepens to 70 and 80 fathoms ; except in the creeks or bays of Dores, Urquhart, Inver Morrison, Cherry ls• land, and the western extremity of the loch. The
depth of water in these varies from 12 to 20 fa. thorns; but even these soundings are so close to the shore, that it has been suggested to lay Mooring Buoys to enable ships to stop for a time ; as it would be quite untafe, especially for ships of great tonnage, to let go au anchor, chiefly from the difficulty of furckoseng or lifting it. Indeed the necessity of ths an these lochs is in a great measure superseded, by the proposed use of the steam-boat for tracking ships; and the anchorage or mooring buoys for large ves sels may now be confined almost entirely to the east and west ersds of the loch ; as the distance to return to either end, in the event of such weather as may prevent the steam tracker from proceeding, cannot be a matter of much moment. The application of steam as a power for impelling ships, is a discovery of the greatest importance to the speedy naviga tion of the Caledonian Canal. Upon the formed banks a tracking-path is readily obtaioed, but along the precipitous shores mad cliffs of the lochs, this would not be so easy a matter; and, even if formed, would not be conveniently brought into use for track ing ships of burden. For although vessels of about 200 or even SOO tons, might tack or 'work in Ness and Loch Lochy, at even for these it would ,be an extremely troublesome operation; and a/to gether impracticable in the ease -of ships of war, Or the largest class of merchant vessels.
There has been much discussion .respecting the sailing of ships on the loch part of navigation. It had been inserted, that the ',lode blow almost oosetasely in a current from the south-west an as to seeder it difficult, if not impossible, to pass by this navigation from the eastern to the western ma. But, upon a more minute attention to the subject, .from the returns or register of she winds, and slate of the weather, by the barometer and thermometer, Inept at Clachnaharry, Fort-Aurstus, and Fort-Wil liam, by order of the Commissioners, since the year 1804 up to the last return of 1816, it appear*, that the winds are nearly as subject to change in the great vale between Inverness and Fort-William, as in other parts of the country.
in the Parliamentary Repo*, the Caledonian Canal is generally laid out in three districts, viz. the Clachnabarry or eastern district, comprehending the work. front Loch Beauly to Fort-Augustus ; the middle district, extending to the west end of Loch Leahy ; and the Consul or western district, from Loch Lochy to Loch Eil, or the western sea. With regard to the middle district, we observe that hitherto the sum annually allowed for this work does not admit of every part being carried on with equal vises& The works of this oempartinest have, therefore, been sismet wholly confined to excavating theironed; it of iospoetrace to have the east ern mad 'opened to Loth Ness„ and the western &I A. aims to Lecii Lathy, hakes much was done to the usreary of the central parts; in order to facilitate the emagrert of materials from she respective seas. This may now be confidently expected to be accom plished, at least for vesaels drawing eight or ten feet water, in the course of the current year, 1817.