Commissioners of Public Works (Ireland): twentieth report with appendices

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Annual Report of Mr. 
Ottley, C.E., 
District Engineer. 

For this purpo.-e 
wc have been fortunate in procuring from the river excavation a large supply of the best sand I have ever seen. 
The position of the Toome excavation is favourable as regards spoil-ground; and we have already made new land to the extent of nearly 10 acres of what was formerly the bed of the lough. 
Several acres more will, no doubt, be created by the material yet to be excavated from the river bed; and all this will, I presume, be disposable for the benefit of the proprietors of lands drained. 
When the works arc finished and the navigation opened, there is no doubt Toome will become a place of much importance, from its central position; and it is satisfactory to observe that its noble proprietor, Lord O'Neil, has done much of late to beautify and improve it. 

The present bridge of Toomc was erected by ihe late Viscount O'Neil, 70 or 80 years ago, and a heavy toll has been levied on all vehicles passing over it. 

This bridge and toll has, however, been recently purchased (under a special statute) by the counties of Antrim and Derry, and the public have had free passage over it since the 5th of November last. 
This desirable arrangement was brought about by the timely suggestion of the Commissioners, on their deciding to construct a new bridge, in lieu of spending nearly an equal sum in the underpinning and repairs of ihe old one, which is in every way inconvenient and ill-designed. 
The grand juries at once entered into the Board's views, and the bridge has accordingly become the property of the two counties, as before described. 
The following exhibits the greater portion of the work done on the 4th division in 1851:— 

Excavation Slope paved Stone dressed Masonry built 

189,296 cubic yards. 
1,900 superficial yards. 
27,788 cubic feet. 

984 cubic yards. 

the most important source of supply to to bo expended than on any other of the of our operations at the south end of the 

This important branch of the district has been entered upon since my last annual report; and the following description of the work done will show that the progress of the year has been very considerable. 
The Blackwater, with its catchment, forming Lough Neagh, and upon which more is designed tributaries, formed almost, exclusively the scene lough. 
The Blackwater discharges the waters from 620 square miles of country, and that discharge in time of flood reaches 500,000 cubic feet per minute. 
The channel of the river for 5 miles up from Lough Neagh is sufficiently capacious, but thence to Charlemont aud Blackwater Town it is not so. 
Its deficiency was caused by sharp bends in its course, and a number of shoals, not separately important, but by their frequency causing serious obstruction. 
The first operation on theopening of the working season was to commence excavating a straight new channel at the several points where objectionable bends existed, and in the course of the season four such new portions of channel were completed, with bottom breadths of 80 to 90 feet, and a minimum depth of 6 feet below the intended summer water of Lough Neagh. 
The material from these excavations has been applied to filling up the old river-course, and very little lo^s of land will result. 
The very low character of the flooded lands along the Bhickwater made it necessary to provide against their inundation from tho river itself in sudden floods (irrespective of Lough Neagh), by a system of embankments along its sides extending from Vomer's Bridge up to Moy, and a sufficient number of self-acting sluices in connexion with them. 
These embankments, to the extent of three miles along the Tyrone side of the river, from Moy down to Goodlatte's Ferry, have been completed, and three sluices constructed through them for drainage purposes. 
Up to to the close of the year these banks and sluices (coupled with the low level of Lough Neagh) had proved entirely effective, and efforts would have been made to extend the embankments, but a feeling arose amongst a few of the proprietors, that the total relief of their lands from fioodings was not desirable, and having stated their opinions that the work already done on the Lower Bann had sufficiently relieved these lands, the banking of their property from the Blackwater was, at their urgent request, temporarily deferred. 
On the Armagh side of the river a length of embankment has also been made, extending from the Ulster Canal to the junction of the Callan River; but as the Callan itself is not kept within its banks, and is not intended to be retained in its present course, the land on the Armagh side of the Blackwafer has not been altogether freed from overflow. 
Tho original design, as regards the improvement of tho low lands along the Tall and Callan rivers, has been recently departed from, and a plan has been approved whereby those lands will be much more perfectly drained than they could have been were the first devised proposition adhered to. 
Instead of depending on embankments if is now decided to divert the Tall and Callan rivers altogether, and carry them by ono direct course through Sir William Vomer's bog so as to flow into the Blackwater at Vomer's Bridge, a point 5miles farther down the stream than the present confluence. 
The two great features in favour of this change in the design are,—lst. 
The fact that the level of flood-water at Verner's Bridge, where the new Tall and Callan will discharge,