10 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



feemed (with the sanction of tlie officers) to meet with the entire approval of 

 the board : but by this time the civil engineers bcforementioned had 

 brought in their voluminous and conclusive report, stating, that Woolwich 

 was unfit for the purpose of his Majesty's Ordinary, and that the sediment off 

 M'oolwich Dockyard had so accumulated of late years, that it «ould take a 

 period of five years to remove it, and that at an outlay of at least 152,0001. ; 

 and after all it would be so uncertain in its efl'ccts, that they declined entering 

 into any further particulars, but recommended its being abandoned altogether, 

 and that the Naval Dockyard should be established at Northfleet. 



It is well known to every member in both houses of Parliament, at 

 that period, with what violence the propriety of this immense work 

 was agitated, which was estimated at the vast sum of seven millions 

 sterling, or upwards. Pamphlets were written on the subject and circulated 

 in all directions ; one, I believe, by the late Lord Melville ; another by 

 tho late George Rose, Esq.; a:id several others. We had, however, 

 the satisfaction of being addressed officially, by the Navy Board, request- 

 ing us to send them our report to have it compared in all its bearings with the 

 detailed reports of the engineers beforemcntioned ; with this we of course 

 complied, and offered, in open contradiction to our opponents, to reinstate the 

 harbour in eighteen months. This proposition and statement (so much at vari- 

 with those of the other engineers) astonished the Navy Board, and they 

 (inally declined to decide on the eligibility of one report or the utility of the 

 other ; and with this impression, I believe, they laid the whole business before 

 the Admiralty Board. 1 ought to add, that the plan of the new Dockyard 

 (ind naval arsenal at NorthHcet, was in such a state of forwardness, that 

 the land at Northfleet for the intended docks was actually purchased by 

 Government, and it was at one time fully expected that the works were to 

 commence. But, notwithstanding all these preparations, the Board of Admi- 

 ralty decided in favour of tho mud engineers, with which name we were 

 honoured in some of the pamphlets of that date. The grand work at North- 

 fleet was consequently abandoned, and we, in the end, entered into a contract 

 with the Navy Board, whereby we undertook to restore the Woolwich moor- 

 ings to their former slate. How far this has been accomplished may be 

 easily ascertained hy application to Mr, Cunningham, who, 1 believe, at one 

 time, much to his credit, stood alone unsupported against the opinion of those 

 engineers who advocated the abandonment of the Dockyard at Woolwich. 



John Hi'ghes. 



The preceding extract will show that the first steam dredging engine 

 with frames, links, and buckets, was used by my father in the year 

 180-t, in a contract under the Corporation of the Trinity House, at the 

 moorings opposite the East India Dock gates. 



Of the advantages that have been derived by the Government and 

 shipping interests of this kingdom, from the means afforded by the 

 Bteam diedging machine, of deepening and clearing the various har- 

 bours, I am quite unable to give anything like an adequate idea. 

 With respect, however, to its application by the civil engineer to the 

 numerous operations connected with the improvement of navigation, 

 it is quite certain, according to the experience of upwards of thirty 

 years, since its first introduction, that a more eftective and necessary 

 machine has never been placed under his command. 



I propose noiv to notice the further improvements that were made 

 in the steam dredging engine under my own inspection, whilst 

 managing the dredging operations on the Caledonian Canal, under my 

 late uncle, Mr. William Hughes. In order to convey a proper idea of 

 the great value of the system of steam dredging, as practised on this 

 important work, it will be necessary to give seme description of the 

 nature of the country through which the canal is carried, from which 

 it will be seen that difhculties almost insurmountable would have 

 occurred to impede the execution of the canal, had not the dredging 

 proved effectual to the full e.vtent of the most sanguine anticipation. 



The line of country wliich had been fi.\ed on for the course of the 

 canal, comprised three deep and extensive lochs or lakes, extending 

 longitudinally with the canal for the length of thirty-seven miles and 

 a half, whilst a distar.ce of about twenty-three miles intervened 

 between the lakes. Thus it was necessary, in order to complete the 

 communication between the eastern and western shores of Scotland, 

 to excavate between one lake and the oilier, and afterwards to deepen 

 all the shallows that occurred in the direction through which the canal 

 was to be carried. 



The method of dredging which had been pursued by my father, as 

 before described, on the river Thames, and subsequently by Mr. 

 Eeniiie at the Hull docks, was found perfectly successful in every situa- 

 tion where the machine could float above the spot at which the 

 dredging was required. The position of the buckets, however, required 

 considerable alteration before tho engine could be rendered capable of 

 cutting her way across a neck of laud, or througli the various .shoals 

 which occurred on many parts of the lakes. It was accordingly 

 found necessary so to construct and fix the ladder or bucket frame, 

 that when lowered to the working position it projected several feet 

 beyond the bows or stem of the vessel — an exjieriment, of which the 

 ultimate success was at the time considered very doubtful, and con- 

 cerning which great anxiety was felt by all those interested in the 

 proceedings. It, therefore, afforded universal and infinite satisfaction 



to find that the engine worked with the irjost perfect ease, cutting a 

 passage on the very first trial out of a piece of the canal (which had 

 previously been filled with water for the purpose of floating her) 

 through a neck of land into the eastern end of Loch Docli Four. 

 This work having been accomplished, the engine was successfully em- 

 ployed in removing several extensive shoals which occurred in the lake. 

 At the eastern end of Loch Doch Four where the water fiom Loch 

 Ness falls into it, close to the ruins of Old Ness Castle, occurred 

 perhaps the most diflicolt case of dredging that can well be imagined. 

 This was occasioned by the necessity of carrying the canal along the 

 bed of the river Nes.s, which discharges tlie water from Loch Ness 

 into the lower level of Loch Doch Four. The bed of the river was 

 composed of an exceedingly hard stratification known by the term 

 monntain-clay : and it would be diflScult to conceive anything more 

 calculated to resist all eflxirts to remove it than this very compact and 

 almost impenetrable substance. It occurs in great masses almost with- 

 out any appearance of stratification, and entirely free from vertical 

 cracks or fissures. Gunpowder applied in the ordinary mode of blasting 

 was found to produce little or no effect on this clay, as it blew out 

 of the orifice made to receive it without loosening any quantity of the 

 mass. 



The river Ness flowing over this primitive and hitherto undisturbed 

 bed, falls into Loch Doch Four with rather a rapid current, and against 

 this the engine had to light her way, while the duty to be performed 

 w.ts the excavation of the river-bed, to a depth varying from four to 

 twelve feet, and very often the sides had to be widened, and in places 

 where considerable bends occurred in the course of the river, a new 

 channel had to be formed with a breadth at bottom of fifty feet accord- 

 ing to the regular section of the canal. It was soon evident when the 

 engine was set to work against the current, and required to tear up tlie 

 hard bed of tlie river, that the exercise of every possible contrivance 

 was necessary in order to the fulfilment of this difficult task. 



It was at first found impossible to keep the vessel, containing the 

 engine, steadily moored against the current, in consequence of the slip- 

 ping and giving way of chains, cables, and anchors. The machinery, 

 which was of the very best description, and constructed by the Messrs. 

 Donkln, was quite unable to withstand the immense force applied to 

 it. in order to make the buckets cut into and bring up the excavated 

 clay. All the ground tackle, comprising a full complement of anchors, 

 cables, and hawsers, was first-rate, both in workmanship and materials ; 

 tho links were of the best Swedish iron ; all the bolt-holes were steel- 

 bushed; while the bolts themselves were of the best tempered steel, and 

 case-hardened. 



The whole of the buckets were not only made of the best Swedish 

 plate-iron, but had strong pieces of tempered steel -plate riveted to their 

 edges. The friction-blocks throughout the engine were manufactured 

 and fixed with most surpassing care, and could always be adjusted to 

 act with the greatest nicety. Notwithstanding, however, all the per- 

 fection of this engine, and the constant care with which every operation 

 was performed, tlie most vexatious and apparently insurmountable in- 

 efficiency, v.'as the result of her first labours in the situation above de- 

 scribed. It was no uncommon occurrence to witness, in rapid succes- 

 sion, the tearing away of the buckets, the stripping of the cogs from off 

 the wheels, the snapping of the chains, breaking of bolts, and giving way 

 of the anchors and cables, while on more than one occasion the whole 

 string of chain, buckets, and bolts, was carried overboard. 



No sooner were the necessary repairs executed upon the shattered 

 machinery than it was again torn to pieces, and after all no impression 

 was made, no effect produced, on the solid and obstinately resisting 

 mass, against which the engine was contending. Without dwelling upon 

 the various unsuccessful contrivances which were introduced, it will be 

 sufficient to mention at once, that none of these proved effiictual until 

 the expedient was tried of removing every alternate bucket from off 

 the chain, and fixing, instead of it, two cittters formed of plates of 

 iron and hardened with steel, which projected at right angles to the 

 line of the chain, and, as this revolved, cut vertically into the ground 

 below. Each pair of cutters, therefore, effected two simultaneous 

 incisions longitudinally in the direction of the vessel, and the lip of 

 the succeeding bucket descending immediately afterwards, scoops up 

 the mass separated by the cutters, and carries it to the top of the 

 frame. After this alteration the work of the engine was performed 

 with much greater efficiency than before ; but, in consequence of the 

 hard and incompressible natureof the clay above described, the counter 

 resistance offered to the buckets and cutters would have been sufficient 

 to tear them off' and otherwise derange the machinery, had this not 

 been prevented by the action of the friction-blocks. By means of 

 these, whcuever a visible tightening and straining of the chain 

 throughout its whole length, denoted that some extraordinary resist- 

 ance was opposed to the motion of the buckets, the engine continued 

 to work and the wheels to revolve, while the chain and buckets re- 



