1881 Institution of Mechanical Engineers: Visits to Works
Note: This is a sub-section of 1881 Institution of Mechanical Engineers
Visits to Works (Excursions) in the Newcastle-upon-Tyne area
Works opened to the members
The following Works, &c., in Newcastle and Sunderland, and in their neighbourhood, were thrown open to the members in the course of the week:—
- Sir W. G. Armstrong and Co. Engineering and Ordnance Works.
- Robert Stephenson and Co. Engineering Works.
- R. and W. Hawthorn. Engineering Works.
- J. and G. Joicey. Engineering Works..
- Donkin and Nichol. Engineering Works.
- Walkers, Parker, Walker, and Co. Lead Works.
- M. and M. W. Lambert. Printing and Bookbinding.
- Andrew Reid. Printing, Engraving, etc.
- Newcastle Chronicle Office. Newspaper Printing.
- T. and W. Smith. Hemp and Wire Rope Works.
- Henry Angus and Co. Coach-building Works.
- Atkinson and Philipson. Coach-building Works.
- North Eastern Railway Works. Engineering Works.
- John Abbot and Co Iron and Engineering Works.
- R. S. Newell Wire Rope Works.
- Haggie Brothers Hemp and Wire Rope Works.
- Black, Hawthorn, and Co. Engineering Works.
- Clarke, Chapman, and Gurney. Engineering Works.
- Hawks, Crawshay, and Sons. Iron and Engineering Works.
- Newcastle Chemical Works Co. Chemical Works.
- Tyne Improvement Commissioners. Newcastle Swing Bridge.
- Tyne Improvement Commissioners. Howdon Repairing Shops and Slipways.
- Tyne Improvement Commissioners. Coble Dene Dock (under construction).
- Tyne Improvement Commissioners. Sculls Shields, South Pier (under construction).
- Tyne Improvement Commissioners. Tynemouth, North Pier (under construction).
- J. T. Eltringham. Engineering Works.
- Jarrow Chemical Co. Chemical Works.
- John Readhead and Co. Shipbuilding and Engineering Works.
- J. P. Rennoldson. Engineering Works.
- Hepple and Co. Engineering Works.
- Andrew Leslie and Co. Shipbuilding Works.
- Charles Tennant and Co. Chemical Works.
- Foster, Blockett, and Wilson. Lead Works.
- Palmer's Shipbuilding Co. Shipbuilding, Engineering, and Iron Works.
- Swan and Hunter. Shipbuilding Works.
- Schlesinger, Davis, and Co. Shipbuilding Works.
- Wallsend Slipway and Engineering Co. Engineering and Ship Repairing Works.
- C. Mitchell and Co. Shipbuilding Works.
- Wigham Richardson and Co. Shipbuilding and Engineering Works.
- Tyne Iron Shipbuilding Co. Shipbuilding Works.
- Cookson and Co. Lead Works.
- Tharsis Copper Co. Copper Works.
- John Spencer and Sons. Steel Works.
- Robert Thompson and Sons. Shipbuilding Works.
- J. L. Thompson and Sons. Shipbuilding Works.
- James Laing. Shipbuilding Works.
- George Clark. Engine Works.
- Armstrong, Addison, and Co. Timber Preserving Works.
- William Doxford and Sons. Shipbuilding and Engineering Works.
- John Blumer and Co. Shipbuilding Works.
- S. P. Austin and Son. Shipbuilding and Repairing Works.
- Strand Slipway Co. Shipbuilding Works.
- Short Brothers. Shipbuilding Works.
- Osbourne, Graham, and Co. Shipbuilding Works.
- Bartram, Haswell, and Co. Shipbuilding Works.
- John Dickinson. Marine Engine Works.
- C. H. Reed and Co. Forge, Chain, and Anchor Works.
- S. Tyzack and Co. Iron Works and Rolling Mills.
- J. and E. Lumsdon. Forge, Chain, and Anchor Works.
- Ford Paper Works.
- Hendon Paper Works.
- Southwick Pottery.
- Sunderland Gas Works.
- Sunderland and South Shields Water Works.
- Weardale Iron and Coal Co. Rolling Mills.
- Consett Iron Co. Rolling Mills.
Tuesday 2nd August
On the afternoon of TUESDAY, 2nd August, the Members were entertained at luncheon by the Local Committee, at the Assembly Rooms. They were then conveyed by special train to Elswick, to visit the works of Sir W. G. Armstrong & Co. The party were received by Sir William Armstrong, Mr. George Rendel, and Mr. Percy Westmacott, and were conducted over the works. The party then divided, one section going on by special train to visit the Newburn Steel Works of Messrs. John Spencer and Sons, and the other returning by special steamer to inspect the Swing Bridge at Newcastle, the opening and closing of which were exhibited. For a description of the bridge see notice below of the Elswick Works. At Newborn the party were received and entertained by Mr. John W. Spencer, and went over the whole of the works.
In the evening the Members were splendidly entertained by Sir W. G. Armstrong, Past-President, in the Banqueting Hall, Jesmond Dene.
W. G. Armstrong and Co
ELSWICK ENGINE AND ORDNANCE WORKS, NEWCASTLE-ON-TYNE
W. G. Armstrong and Co
N.B. The following notice of these works is mainly condensed from articles in The Regions, July 1881, reprints of which, presented by the kindness of the proprietors, were distributed to the Members at the time of the visit.
The Elswick Engine Works, started in 1847, owe their origin to Sir William Armstrong's success in the development of water- pressure machinery; similarly the manufacture of ordnance grew up in consequence of his having brought out his system of ordnance. The former 1Fanch of the works preceded the latter by about ten years, and therefore should be first noticed.
The hydraulic machinery* manufactured at the Elswick Works consists chiefly of cranes, hoists, capstans for railway stations and docks, rotary engines, pumping engines, opening bridges—swing, draw, and lift—machinery for opening and closing dock gates and sluices, bands and elevators for discharging and storing grain, hydraulic pumps, winding engines for mines, &c. &c. In addition to these there are the steam pumping engines, with boilers and accumulators, for supplying the water under pressure.
For papers dealing with this machinery see Proceedings 1858, 1868, 1869, 1874.
The ordinary forms of hydraulic cranes and hoists, as used in docks, railway stations, warehouses, &c., are so well known that any detailed description of the several varieties is unnecessary. In nearly all cases where the lifting power does not exceed 30 tons, the hoisting apparatus consists of a cylinder and plunger acting on the lifting chain through a system of fixed and moveable pulleys, which multiply the travel of the plunger to the extent required. By this means the necessity for any gearing, brakes, pawls, and clutches is avoided, and the working of the crane is rendered very simple and safe. The lifting machinery is usually placed in the revolving pillar of the crane itself, so as to economise space and cost of foundations. For dock purposes the crane is usually mounted on a pedestal of wrought iron about 8 ft. or 10 ft. high, so as to give the jib clearance over a ship's side; and this pedestal is provided with wheels, so that four or five cranes can be brought to bear upon the several hatchways of one vessel. These cranes are either counterweighted or clamped to the rails when at work, as may be most convenient. The connections to the pressure and return mains are made by sliding or jointed pipes, attached to hydrants inserted at intervals in the main pipes.
When a lifting power of from 30 tons to 80 or 100 tons is required, a rotary hydraulic engine, acting on an ordinary chain purchase by means of gearing and a "cupped-drum," is usually employed, and the general construction of the crane is modified by a circular roller path with live or fixed rollers being substituted for the iron pedestal. For very heavy cranes, to lift loads of 80 tons to 100 tons and upwards, Sir W. G. Armstrong and Co. now use a direct- acting cylinder of from 40 ft. to 54 ft. stroke, suspended in gimbals from the end of the jib, and fitted with a piston and rod, by which the load is lifted and lowered without the intervention of chains or gearing. These cranes are on "live" rollers, and are turned by a rotary hydraulic engine acting on a rack attached to the roller path. An independent chain purchase, worked by the slowing engines, is provided for lifting loads up to 12 or 14 tons.
Hoists for shipping coal are much made at Elswick, for South Wales and other ports where the railways approach the docks at a low level. The lifting cylinders are usually direct-acting, and, with a view to economy in the consumption of power, are so arranged that on the down stroke the weight of the cradle and empty truck is made use of, to force back the water from one of the cylinders into the accumulator.
Hydraulic capstans are very much used, not only for docks, but also for hauling trucks in railway goods stations, and in connection with coal hoists. The bed-plate carrying the capstan-head and engine is mounted in trunnions in a cast-iron casing, and can be turned over when access is required to the engine. The casing is bedded in the ground, and scarcely any foundation is required. Sir W. G. Armstrong and Co. are now introducing a new pattern of engine for this class of work, which acts directly on the capstan-shaft, and is fitted with a valve common to the three cylinders.
Swing bridges may be divided into two classes — one in which the bridge is lifted bodily from its bearings by a hydraulic press before being swung round, and the other in which the bridge is permanently on rollers, either fixed or "live." The combined road and rail way bridge erected by Sir W. G. Armstrong & Co. over the 100 ft. entrance to the Queen's Dock at Glasgow, under the direction of Mr. Deas, the engineer to the Clyde Trust, is a good example of the first class.
There are two main girders, curved on the top, each 181 ft. long, and 25 ft. deep over the centre of motion. The width between the main girders is 23 ft. 6 in., and there is a cantilever footway 5 ft. 3 in. wide on each side. The hydraulic press is 5 ft. 3 in. diameter, and acts on a transverse box girder, riveted to the underside of the main girders. The bridge is turned by a pair of hydraulic cylinders, acting through chains on a drum fixed to the underside of the bridge. This bridge is designed for very heavy road and railway traffic, and the total weight of the moving parts, including counterweight, is about 750 tons.
The swing bridge over the Tyne at Newcastle may be taken as an example of the second class, namely that in which the bridge is permanently on its bearings. This bridge is for road traffic, and when open leaves two passages each 100 ft. wide, one on either side of the centre. The main girders are each 277 ft. long and 24 ft. deep at the centre. The roadway is paved with wood, and has a clear width of 23 ft. 9 in. There are in addition cantilever footways 9 ft. wide outside each main girder. The bridge turns on forty-two "live" rollers of cast-iron hooped with steel. The roller paths are of cast-iron, the lower being bedded on the masonry of the central pier, and the upper bolted to an annular box girder on the underside of the main girders. The total weight of the moving parts of the bridge is about 1400 tons; and in order to diminish the pressure on the rollers a hydraulic press is provided at the centre of motion, which exerts a constant upward pressure of about 800 tons, thus relieving the rollers to this extent.
The turning machinery is entirely in duplicate, and is on the central pier. There are two steam pumping-engines, each of 20 horse-power, two multi-tubular boilers, and two accumulators, which are placed in two of the foundation cylinders. There are two hydraulic rotary engines, each of 60 horse-power, acting through gear on a rack bolted to the upper roller path. The teeth of this rack are 13 in. wide and 9 in. pitch. The apparatus for setting up the nose ends of the bridge is worked by hydraulic power, and consists of two pairs of hydraulic presses with rams acting downwards on the abutments, and the same number of horizontal sliding blocks. When the nose ends of the bridge are over the abutments, the girders are slightly lifted, and the sliding blocks inserted between them and the resting plates on the abutments. The water is then exhausted from the presses, and the ends of the girders rest on the blocks. The valve house, from which all the motions of turning &c. are controlled, is placed on the overhead platform, which connects the main girders. Above this house is a dioptric light of the 7th order.
The bridge is approached by two fixed spans, of 99 ft. and 80 ft. respectively. This work was carried out under the direction of the engineers to the Tyne Commission, Mr. J. F. Ure and Mr. P. J. Messent. Another variety of the opening bridge is the drawbridge, or rolling bridge, which is used where the site is not suited for a turning bridge. The operation of opening one of these bridges consists lifting it from its bearings until the underside is above the level of the roadway or quay, and then running it back on the roadway. The bridge is lifted by a pair of hydraulic presses near the quay edge, one under each main girder. The rains of these presses are furnished with rollers, on which, and on other fixed rollers at the rear end, the bridge is run back, a suitable roller path being fixed to the underside of the main girders. The bridge is run in and out by a pair of hydraulic cylinders. Sir W. G. Armstrong & Co. are now erecting a bridge of this class, with a span of 90 ft., over the entrance to the Kattendyk Basin at Antwerp. The length of this bridge, which is designed for both road and railway traffic, is 159 ft., and the width 30 ft. over all. There are two main girders, each 9 ft. deep. The total weight of the moving parts, including counterweight, is about 350 tons.
The lifting presses are each 31 5/16in. diameter, and 3 ft. 2 in. stroke, and are hooped with steel. The rollers are 3 ft. 6 in. diameter, and 9 in. wide, and are also hooped with steel, and the roller path on the bridge is of the same material. The hauling cylinders are placed below the rear end of the bridge.
For opening and closing dock gates, four forms of apparatus are commonly used. The first consists of a cylinder fixed at the back of the wall below the quay level, and fitted with a plunger and multiplying sheaves as in a crane or hoist, the chain being attached at one end to the cylinder and at the other to the gate. Two such cylinders are required for each gate, one to open and the other to close. In the second form the chains are passed over a crab provided either with an ordinary barrel or with a cupped drum, and driven by a rotary hydraulic engine.
At the new Langton Docks, under the direction of Mr. Lyster, the machines for closing the gates have been furnished with spiral drums, so as to take up the slack chain quickly and without waste of power. The third form is a modification of that last described. The chains, instead of being fixed to the gates, are attached to the lock walls, and pass over guide sheaves on the gates and above the heel-posts to the crab, which is placed in a chamber in the quay as near the heel-post as convenient. By this device the crabs for the opening and closing chains can be placed side by side and worked by one hydraulic engine. The necessity for chainways through the walls is also avoided, and the foundation work is much simplified. In the fourth form the gate machines and capstans are connected by shafting, or two or more gates and capstans are driven by one hydraulic engine.
The simplest and best form of hydraulic machine for opening and closing sluices is a cylinder fixed vertically over the paddle or sluice-door, and fitted with a piston and a piston-rod or plunger attached to the paddle. A hand force pump, either fixed or movable, is usually provided, for working the sluice by hand when required. In some cases a screw is used instead of a hydraulic cylinder, the nut being driven by a hydraulic engine.
The steam pumping engines which supply the water under pressure for working hydraulic machinery are for the most part horizontal, and the pumps are in the same line with the cylinders, and worked directly from the steam pistons, the piston-rods being prolonged backwards. Condensers, either jet or surface, are usually supplied with the larger engines, which are often constructed on the compound principle. An air vessel is sometimes substituted for a weighted accumulator. This plan was adopted in the case of the machinery for some hopper barges on the Tyne, the first of which was constructed in the year 1865, and has subsequently been carried out in several cases ashore and afloat.
The Ordnance Works are now to be described. In the original system of ordnance, introduced by Sir William Armstrong about 1858, the chief features were rifling, breech loading, and the application of coils shrunk over each other systematically. In the ordinary gun now constructed at Elswick this system of construction is still adhered to. At a later date however muzzle-loading came into favour, and muzzle-loaders are also constructed at Elswick, the coil system being retained. In February, 1878, a new type 6-in. gun of 78 cwt. was issued from Elswick, which was fired with charges about half the weight of the shot, giving to a projectile weighing 70 lb. a velocity of nearly 2200 ft. per second. In January, 1879, 8-in. muzzle-loading and breech-loading new type guns were submitted to the Government for trial. The great development of power in these guns is due to increased length, slow-burning charges, and a specified allowance of air space in the powder chamber. In July, 1878, an Elswick new typo 8-in. gun of 11.5 tons fired a 180-1b. projectile with over 2200 ft. velocity. This increase in length in ordnance is favourable to breech-loading, and in certain cases it would appear that breech-loading will enable guns of greater power to be employed than was possible with muzzle-loaders. The case of broadside guns for ships is a case in point. The breech-closing arrangement employed at Elswick is that now adopted in the British service.
The newest and most interesting gun constructed at Elswick is made almost wholly of steel, consisting of an inner steel tube, on which are wound coils of steel riband, with the tension on each concentric layer adjusted to agree with the results obtained by calculation. This is done by means of a machine designed for the purpose. The advantage of the riband gun is threefold— (1) that steel may be obtained in small section with greater strength than is possible in any other form; (2) that each layer can be brought more truly to its correct tension; (3) that the danger due to the existence of flaws becomes reduced to a minimum, because a flaw would be easily detected, and, if not detected, would be confined to the riband in which it existed. To give longitudinal strength, a certain number of layers are formed by short lengths of steel riband placed longitudinally like the staves of a barrel, and secured by doubling or hooking in the ends. The whole is cased with thin steel; one or two wrought-iron coils only are used on the entire gun. A 6-in. gun has been made on this system and fired, and it has given results far surpassing any that have yet been obtained with guns of the same weight; a 10-in. gun is nearly complete.
For some time after the introduction of rifled ordnance, very little improvement was attempted in carriages. In 1865 however iron carriages came in, and the Elswick Works turned out some early patterns. One pattern of disappearing carriage, differing from that of Moncrieff, and acting by hydraulic power, was designed at Elswick, and supplied to H.M.S. Tameraire. The application of hydraulic machinery to replace hand power has been specially advocated at Elswick, and is adopted there whenever it is possible. A special arrangement is also in use by which muzzle-loading guns, mounted to fire en barbette, may be loaded under cover. This is effected by running the gun round on its traversing platform until it is parallel to the parapet, when its muzzle is dipped so as to bring it in line with a rammer in a fixed position, with charge and projectile presented ready for loading; and the gun, thus depressed, forms an incline, up which they are easily pushed home.
The traversing platform rests on three points, not four: namely the two trucks, and a cap pivoting on the centre of the training circle. The gain is very great, for while a bearing on four points is constantly disturbed by the want of truth in the planes which contain the four points, a bearing on three points is always true.
The Elswick 100-ton muzzle-loading gun, as mounted for Malta and Gibraltar, is the largest example of a muzzle-loading gun firing en barbette on this system. The principle of keeping the centre of gravity of the mass nearly over the traversing centre is observed, while the employment of the gun as an inclined plane for running the shot up to its seat in the bore is applied to considerable purpose in the case of a projectile weighing 2000 lbs. The accumulator and engine are below ground. The accumulator is weighted to a pressure of 75 lbs. per sq. in., and is worked by an ordinary steam sapper of 6 horse-power. It can also be pumped up by forty men with hand- pump gear, in which case it is calculated that the gun can be fired at the rate of one round in about 7;12- minutes.
One other design should be mentioned, namely a mountain gun unscrewing into two parts at the trunnion ring. This device enables a field gun of considerable power to act as a mountain gun, instead of the short feeble weapon previously used. These guns have abundantly proved their value in Afghanistan.
The Elswick Works cover an area of ground lying between the river Tyne and the Newcastle and Carlisle Railway. The east end is devoted chiefly to ordnance work, the west end being the so-called engine works, where the engineering structures and hydraulic machinery are made. The offices are between these two departments, and the principal road and jetty are near the middle point.
Commencing with the Ordnance Works, at the N.E. corner, the first objects of interest are the 6-in. and 40-ton breech-loading guns, mounted to illustrate the "protected barbette" system of working guns, and also the system of working breech-loading guns in turrets by hydraulic power.
Close to these guns is a shrinking-pit for ordnance; also nineteen gas-producers for furnaces.
The shops may then be taken in the following order.
Coiling Shop:—The largest section of bar coiled has been 12 in. by 10 in.; length of coiling furnace, 180 ft.; there is a gas furnace for heating barrels, also for tempering, with an oil well 50 ft. deep, over which stands a hydraulic hoist.
Forge:— The largest hammer, by Thwaites and Carbutt, Bradford, has a 48 in. cylinder and 12 ft. stroke; weight of piston and hammer head, 35 tons.
Blast Furnaces:— One furnace building, two in work, and running from 1100 to 1200 tons a week, chiefly Nos. 1, 2, and 3 pig, made from Spanish and Elba ores; most of it is sold for steel snaking. The blast is at present heated by horseshoe pipes, but Cowper's heating stoves are in course of erection; present temperature of blast about 900° Fahr.
Carriage Shed:— Band saws cutting iron may be noticed, and the Albini carriage on short-recoil and self-running-up system.
Projectile Store, containing finished projectiles:— These are chiefly made with bands only of the full diameter, which saves work and leaves to the projectile body the strength of the uninjured skin of the casting. The Palliser chilled projectiles have generally sharp-pointed heads, struck with a radius of two diameters. Foundry, containing ten cupola furnaces, of which four are generally in work:— Forty tons is about the maximum weight of casting made in the foundry; a much larger casting, namely the bed of the steam hammer, weighing 137 tons, was cast on its own ground.
The hydraulic cranes are fixed so as to work in pairs or three together for heavy work.
Engines:— Horizontal double Corliss engines are generally employed, with multi-tubular boilers. Juckes's bars and system of stoking are applied to all.
Jetty:— On the east end are two fixed hydraulic cranes for lifting 5 tons and 30 cwt.; and between them are large hydraulic shears, worked by a direct-acting hydraulic cylinder, 40-ft. stroke, lifting 120 tons. The back leg moves so as to bring the lifting cylinder about 30 ft. beyond the face of the quay. The foot is moved by a screw 50 ft. long, with hydraulic engine and gear, giving three different powers. Along the jetty run pipes with hydrants from 18 ft. to 36 ft. apart, from which work five movable cranes, each lifting about 30 cwt.: these are placed in position to suit the holds of the vessels by means of telescope tubes attached to the nearest hydrants.
Finishing Shop:— The now typo guns should be noticed, together with the breech-loading fittings, and apparatus for firing by electricity and also mechanically.
Turning Shop, for turning, finishing, and boring work, commencing on the solid ingot:—At the east end guns are bored vertically in a pit 23 ft. deep.
Large Tool Shop, for turning, boring, and rifling:— The finest lathe is one of Whitworth's, for turning, boring, screw-cutting, and rifling, taking a job 44 ft. in length, 36 in. centres. There is also a convenient one, designed at Elswick, and made by Fairbairn Kennedy and Naylor, taking a chuck job 20 ft. in diameter and 4 ft. 6 in. long, or a job 34 ft. long and 8 ft. in diameter; it is fitted with slide-rests on independent beds. Forge:—Crank-shaft and gun work, coil welding, &c., are performed. The steam hammers are from 24 tons to 15 cwt.
Small Tool Shop, turning and boring out short coils:— There is a large endless band saw 11 in. wide, which cuts directly through iron cylindrical work about 16 in. in diameter. Its speed is from 76 ft. to 129 ft. per minute.
In the Engine Works the shops may be taken in the following order.
Bridge and Boiler Yard:— Contains plate-planing, punching, and multiple and radial drilling machines, &c. The work turned out is chiefly crane work and other structural ironwork, such as lighthouses, bridges, dock-gates, pedestals of cranes, &c.
Blacksmiths' Shop:— Boiler and riveting work, Sc., is done here. At the back of the building is the chain-making shop, where all chains for the firm are made, and tested by a hydraulic machine. Two Corliss horizontal engines, working to 190 horse-power each, with boilers and Juckes's grates, Pc., are fixed here, and supply power to the whole engine works.
Fitting and Machine Shop:— The east end of this was the first shop erected at Elswick; planing, boring, drilling, and turning are done here. The west end is used for erecting hydraulic machinery. There is a hydraulic testing machine for testing cylinders and valves up to 3000 lbs. per sq. in. Behind this is the brass foundry. Phosphor-bronze is chiefly employed for gun-carriage work; its cost is considerable, but it works well without lubrication.
Pattern Shop:—In this may be seen working a Richards planing machine, and also circular saws with adjustable spindles, with guide and graduated are for setting work at any required angle. The sawn surfaces are so smooth as to enable planing to be dispensed with.
Erecting Shop, for engines, large cranes, accumulators, &c.
There is a jetty adjoining these works, with 12-ton and 5-ton hydraulic cranes. The works yard is furnished with hydraulic capstans and snatch heads for hauling wagons about the yard, and other appliances. There are five pumping stations with accumulators, supplying hydraulic power throughout the works, at a pressure of about 700 lbs. per sq. in.
Newburn Steel Works
NEWBURN STEEL WORKS
The firm of Messrs. JOHN SPENCER and SONS was established in 1810 by the late Mr. John Spencer, for the manufacture of files. A converting furnace and a mill for rolling steel were erected in the valley at Newburn, where water power was convenient. The water did duty first at the rolling mill, and again lower down on a large breast wheel, 30 ft. diameter, which is still in use for file-grinding. Furnaces for melting the blister steel on Huntsman's plan were also constructed.
For several years files, bar-steel, and best tool-steel were the only manufactures carried on.
On the advent of the locomotive, and the establishment of works for its manufacture, and for that of railway material, the making of springs was commenced here; and for some time the earliest requirements in this line were supplied from these works, which were gradually enlarged to meet the increasing demands of railways. Baillie's volute spring was taken up, and was solely manufactured here for many years in large numbers. The Uchatius process for the manufacture of steel direct from pig-iron by flue granulation in water was tried on a practical scale, and a fine quality of steel was obtained (see Proceedings 1858, p. 146); but its irregularity precluded its adoption at the time.
The manufacture of steel tyres was introduced, casting them in a ring and hammering them on a hick iron; but it was discontinued because of the difficulty then experienced in rolling them. Casting steel in form was commenced here on a large scale in 1866, though for many years previously simple forms had been cast. Messrs. Spencer at that date turned their special attention to this branch of steel manufacture, and they now turn out upwards of 1000 tons per annum of gearing and general castings of steel, in form.
There are three open-hearth furnaces for the manufacture of steel by the Siemens and Siemens-Martin processes, capable of turning out 180 tons per week; two Siemens regenerative crucible-furnaces, each containing 24 pots, besides coke holes, for the manufacture of the finer kinds of steel. There are also eight converting furnaces for the conversion of Swedish bar iron into steel by cementation, their capacity ranging from 15 to 25 tons per heat.
The steel moulding shop is fitted up with hydraulic swing-cranes and overhead travelling cranes, for moulding purposes and for the general requirements of the shop; it covers an area of upwards of 1640 square yards. The forges contain three double-acting steam hammers by Thwaites and Carbutt, of 8 tons, 5 tons, and 2 tons weight, all served by hydraulic cranes and Siemens regenerative furnaces. In the steel tilting-forge are three steam hammers from 30 cwt. downwards.
In the iron forge are a Naylor 30-cwt. steam hammer, and one of 15 cwt. by Thwaites and Carbutt.
The new mill comprises an 18-in. and a 14-in. train, driven by a Corliss engine; and the old mill contains a 10-in. train and guides, worked by an old engine of locomotive typo, by R. and W. Hawthorn.
The manufactures chiefly carried on are steel forgings, steel castings, and bar steel; also various kinds of railway material, such as axles, buffers, springs, and volutes; and files, tool steel, &c. The several shops are built along the valley and on various levels, but are all connected by a railway with one another, and with the Scotswood Newborn and Wylam Railway. A tank engine by R. and W. Hawthorn, and a very useful crane engine by Black Hawthorn and Co., make the transport of material comparatively easy, considering the position and extent of the works.
At Lemington, about one mile nearer Newcastle, are the Tyne Hematite Iron Works belonging to Messrs. Spencer, the oldest ironworks in the North of England; comprising two blast-furnaces, at present out of blast. There is here an old beam engine by Boulton and Watt, dated 1802, which was used for driving a mill and forge. Its beam, showing several imperfections and flaws, was originally considered unsafe, and a spare beam was sent to replace it; however the faulty one stood the Work, and is still in its place. Here were made most of the castings for the permanent way and rolling stock used in the early railway trials of Hedley and Stephenson; and several old patterns still exist, which were shown at Newburn on the occasion of the visit of the Members.
Details Wednesday
Wednesday 3rd August
On the afternoon of WEDNESDAY, 3rd August, the Members visited the offices of the Newcastle Daily Chronicle, through which they were conducted by Mr. Jameson and Mr. R. B. Reed, and witnessed in operation the whole of the machinery and processes described in Mr. Jameson's paper, ante p. 511. Copies of the Chronicle, containing an account of that morning's meeting, were printed off by the Hoe machine, and distributed to the Members.
They then travelled by special train from Newcastle to Jarrow, to visit the works of Palmer's Shipbuilding and Iron Co. The party were received by Mr. C. M. Palmer, M.P., Mr. John Price the General Manager, and the other chief officials, and were most handsomely entertained at luncheon by the Company. They were afterwards divided into several sections and taken through the works, and at 5 p.m. returned by special train to Newcastle.
In the evening the Annual Summer Dinner of the Institution was held in the Assembly Rooms, the President in the chair, and was attended by over 200 Members and guests.
Palmers Shipbuilding and Iron Co
PALMER'S SHIPBUILDING AND IRON WORKS
Palmers Shipbuilding and Iron Co
These works, situated at Jarrow, about six miles below the Tyne Bridge, include within themselves the entire range of operations from the smelting of the ironstone to the complete equipment of iron vessels. The ore itself is brought round by sea from the Company's mines at Port Mulgrave, near Whitby; and is raised from the river wharf at the works up to the railway level, along an inclined plane worked by a stationary engine. Coke and coal come from Marley Hill and other collieries in Durham and Northumberland, by the Pontop and Jarrow Railway; the coke is discharged into a hopper capable of holding about 1500 tons, from the bottom of which the blast-furnace barrows are filled through sliding doors, dispensing with manual labour.
The three blast-furnaces are 85 ft. high, 24 ft. diameter at the boshes, and 81 ft. in the hearth; they are capable of producing together about 1400 tons of pig per week, more than three-fourths of which is used in the works. The blast is heated to about 1100° Fahr. in fifteen cast-iron pipe-stoves; and there are eight kilns for calcining the Cleveland ironstone.
The forges comprise eighty puddling furnaces, producing over 1000 tons of puddled bars weekly. There are two forge engines with 36-in. cylinders, one of 4 ft. and the other of 5 ft. stroke, each driving a roll train and four pairs of 22-in. rolls. There are two plate-mills and ten mill furnaces, producing about 750 tons of finished boiler and ship plates weekly; each mill has two pairs of 24-in. rolls, reversed by clutch and crabs. A bar mill with two pairs of rolls, driven by a 24-in. cylinder, produces 120 tons per week. A fourth mill, with four pairs of rolls, driven by two 30-in. cylinders with 4 ft. stroke, produces about 300 tons of plates per week. There is also a large angle and bar mill, driven by a single engine having 36-in. cylinder and 4 ft. stroke, capable of rolling the very largest angles used in the trade; and also a sheet mill. Attached to the rolling mills are shears, circular saws, punching and straightening presses, and other appliances for the construction of iron ships.
The adjoining department is that of the engine works, which is capable of finishing annually from 30 to 40 pairs of marine engines with their boilers; this department produces its own iron and brass castings, and its own forgings. In the boiler shop, vertical rolls for rolling long boiler shell-plates were first used, and the original set are still in operation.
The shipbuilding department occupies the east end of the works; it contains the largest graving dock on the coast, and also a very fine repairing slip, just newly fitted with hydraulic hauling gear. The building slips are suitable for every kind of vessel up to 500 ft. in length; and are capable, with those in the Howdon branch of the works on the opposite side of the river, of launching 50,000 tons of shipping annually. There are nine building slips at Jarrow and four at Howdon.
The entire works cover more than 100 acres, with a river frontage of about 4,000 ft., and employ about 7,000 persons.
Details Thursday
Thursday 4th August
On THURSDAY, 4th August, the Members were again entertained at luncheon by the General Committee, and afterwards started from the Quayside in three special steamers, on an excursion down the Tyne. They first stopped at Bill Point, to watch the operations of a double dredger, working, not in mud or clay, but in sandstone rock. This dredger is of the ordinary type, but the ladders are fitted at intervals with heavy steel claws, which catch hold of the rock and break it oil. Pieces weighing more than 10 cwts. are frequently brought up on the claws and in the buckets, and the amount raised is 500 tons per day.
The Members then visited the Lead Works of Messrs. Cookson and Co., and the works of the Wallsend Slipway and Engineering Company. At the former the steam desilverising process, and also the sheet-rolling arrangements, described in Mr. N. C. Cookson's paper, ante p. 527, were seen in operation; and at the latter the working of the cradle was inspected, as described in Mr. Boyd's paper, ante p. 581. The Members then landed at the Coble Done Dock Works, described below, where the steam excavators, &c., were seen in operation; and from thence went on to the North Pier at Tynemouth, whence they returned to Newcastle by special train.
In the evening the Members and their friends were invited by the Literary and Philosophical Society, and by the Local Committee, to a Conversazione in the rooms of the Society. The adjoining rooms of the North of England Institute of Mining and Mechanical Engineers, and of the Natural History Society, were also thrown open. A large number of models, pictures, &c., illustrative of the early history of the locomotive, and of the career of George Stephenson, were exhibited, as well as a collection of microscopes. The lecture room was lighted by Swan's electric lamps, and a lecture upon this method of lighting was given by Mr. Swan himself in the course of the evening, Sir William Armstrong occupying the chair.
River Tyne Improvements
RIVER TYNE IMPROVEMENTS
(Abstracted from descriptive Pamphlet by Mr. P. J. MESSENT.)
Previous to 1860 improvements in the Tyne had been limited chiefly to dredging on a small scale, and to groynes and training walls thrown out into the river, behind which land was reclaimed. A bar extending about 800 ft. from west to east, at the mouth of the river, gave at spring tides a depth of 21 ft. and 6 ft. at high and low water respectively, with 600 ft. width of channel. An inner bar with stones occurred at mile above the outer bar; and a little higher the channel was abruptly contracted to 400 ft. width at the Narrows. Shields Harbour, extending about 1 mile up from this point, had a narrow tortuous deep-water channel, with large shoals dry at low water. Thence up to Newcastle were a series of shoals, with only a narrow serpentine channel between them, through which vessels drawing 15 ft. could get up at high-water spring tides, while at low water the depth was only 3 to 4 ft. From Newcastle Bridge to Newburn small craft alone could get up the river, and these only at high water.
In 1853 was commenced, under the late Mr. Plows, the construction of the Northumberland Dock on the north bank, about three miles above the bar, having nearly 55 acres of water space, with 24 and 20 ft. depth over the till, at high water of spring and neap tides respectively. The dock was made by enclosing a portion of a bight in the river, where most of the coal from the Northumberland coalfield was shipped; it was completed in 1857, without the traffic having been stopped during its construction.
In 1856 were commenced the Tyne piers, designed by the late Mr. Walker, at each side of the river mouth. On a base of rubble stone, deposited by barges, is erected a superstructure of concrete and built stonework. The length at present completed of the north pier is 2172 ft. or 0.47 mile, with submerged base extending 350 ft. further; and of the south pier 4495 ft. or 0.85 mile, with 610 ft. of submerged base beyond.
In 1861 authority was obtained for carrying out Mr. J. F. Ure's comprehensive plan for improving the whole 191 miles of the tidal portion of the river, namely 101 miles from the entrance bar up to Newcastle bridge, and 81 miles above the bridge to the boundary stone at Hedwin Streams, midway between Newborn and Wylam. In accordance with this plan, and from the protection afforded by the Tyne piers, the entrance bar has been removed, the former depth of 6 ft. at low water being now increased to more than 20 ft., which is continued up into the harbour at a considerable width; and the obstructive Narrows have been widened from 400 ft. to 670 ft.
In Shields Harbour the dangerous shoals have been removed, and for a length of 11 miles vessels can moor in more than 30 ft. depth at low-water spring tides. Thence up to Newcastle there is now more than 20 ft., depth at low-water spring tides; and for 2. miles further about 18 ft. This is now being continued upwards to Scotswood and Blaydon, where there is already 12 ft. depth at low water. The dredging plant comprises six dredgers (three of over 50 H.P.), ten steam hopper-barges, forty-four wooden hopper-barges without steam power, and six steam tugs, &c.; the whole dredging plant and the repairing establishment have cost £300,000. The quantity dredged from the river bed since 1860 has been sixty million tons. The material dredged is carried two or three miles out to sea by hoppers, and deposited in a depth exceeding 20 fathoms at low water. Near Blaydon the dredged material is spread upon the land; and here the river has been widened from 150 ft. to 400 ft., while a new cut, 400 ft. wide and nearly mile long, has been made through Lemington Point, saving / mile distance between Newborn and Scotswood.
At Newcastle the old stone bridge, which was a great obstruction both to tide and to navigation, has been replaced by a Swing Bridge, completed in 1876, having four openings corresponding with thoso of the High Level bridge immediately above. The two central openings, each of 104 ft., are spanned by a double-ended swing bridge, pivoted on the intermediate or centre pier. The piers and abutments are of stone and concrete, and rest on foundations of cast-iron cylinders filled with concrete, which are sunk to the rock, 45 ft. below low water. The superstructure is of wrought-iron, and was constructed by Sir W. G. Armstrong and Co., as already described, p. 599.
The dangerous bend at Bill Point, on the north bank of the river about 3 miles below the bridge, has now been nearly removed by cutting back the cliff, rising 72 ft. above high water, to a distance of about 400 ft.
Northumberland Dock
Northumberland Dock has been deepened and enlarged, with the addition of a jetty and wharf; below it and outside has been constructed a river-side wharf, 1100 ft. long. Above this are two self-acting coal-shipping staiths, each having three spouts; the loaded wagons, brought within about 540 yards by locomotives, run down inclines to the shipping spouts, and after discharging run off empty down other inclines: with the three spouts from 800 to 1000 tons of coal per hour may be loaded into a vessel at each staith. The staiths were completed in 1874.
Coble Dene Dock
On the north side of the river, below the Northumberland Dock and at the upper end of Shields Harbour, is the new Coble Dene Dock, commenced in 1874, and now within less than two years of completion. It is intended chiefly for import traffic, and will enclose 24 acres of water space, with 3650 ft. of deep-water quays; it will ultimately be extended to join the Northumberland Dock. The tidal entrance will be 80 ft. wide, with a lock 60 ft. wide and 350 ft. long. The depth of high water over the till will be 30 ft. at spring tides, and 26 ft. at neaps. The excavation amounts to about five million tons, of which a large portion is removed by dredgers and steam navvies, and carried out to sea by hoppers; the rest being used to level up the standage ground and the wharves behind the quays.
On the south side of the river, opposite the Northumberland Dock, are timber ponds, enclosing 87 acres and constructed in 1874, for accommodating the timber trade of the port.
The whole of the above works, since 1859, have been carried out for the River Tyne Commissioners, from the designs and under the superintendence first of Mr. Ure, and subsequently of Mr. P. J. Messent, M. Inst. C.E., the present engineer.
Detail Friday
Friday 5th August
On FRIDAY, 5th August, there were two alternative excursions, the first to Sunderland, and the second to the Langley Barony Lead Mines of Messrs. Bewick and Partners.
The first party travelled by special train to Sunderland station, and were thence conveyed in trams drawn by Brown's tramway engine (Proceedings 1880, p. 44) to Wearmouth Colliery (described below), which was inspected under the guidance of Mr. M. W. Parrington, the chief viewer. From thence they drove to the Southwick Engine Works of Mr. George Clark, covering about 31 acres, and entirely devoted to the manufacture of marine engines and boilers. Having inspected these, they crossed the river to the Pallion Shipbuilding Yard and Marine Engine Works of Messrs. Wm. Doxford and Sons, containing five slips, and having plant of the most modern type and construction for the building and engining of vessels of the largest class.
The party then went on board a steamer provided by the River Wear Commissioners, and were taken down to the mouth of the river; passing under the railway bridge erected in 1879, with a clear span of 300 ft., and under the adjoining road bridge, originally built by Rowland Burden in 1796, with six cast- iron arched ribs, and strengthened by Robert Stephenson in 1858 with three wrought-iron tubular arches (Proceedings 1858, p. 261).
At the docks the diamond drill was seen, as employed in boring holes for blasting under water, and some submarine shots were fired. The party then landed at the Chain Cable and Anchor Testing Works of the Commissioners, which were seen in operation; and were subsequently received by Mr. James Laing, Chairman of the Board, the Commissioners, and the principal members of their staff, and were conducted by them over the docks, inspecting the working of the coal staiths, the hydraulic machinery at the new Sea Lock, &c.
They were then most handsomely entertained at dinner by the Engineers and Shipbuilders of Sunderland, in one of the Commissioners' large warehouses on the quay (specially adapted for this occasion); and returned to Newcastle in the course of the evening.
Wearmouth Colliery
WEARMOUTH COLLIERY, MONKWEARMOUTH.
Wearmouth Colliery
The sinking of this colliery was commenced in 1826 and continued without intermission for nine years, reaching the Maudlin or Bensham seam in 1835, at a depth of 532 yards from the surface. In passing through the magnesian limestone, feeders of water amounting to 2000 gallons per minute were met with, and pumped to the surface; until at a depth of 140 yards a suitable foundation was met with, and the water shut out by means of metal tubbing. The pits were some years afterwards sunk to the Hutton seam, which was passed through at a depth of 574 yards.
The temperature of the coal seam at this depth is found to be 90° Fahr.; but by means of a constant supply of fresh air the atmosphere iu the workings is reduced to a mean temperature of 75°. The total ventilating current amounts to 200,000 cub. ft. of air per minute, which is produced by means of a furnace having a fire-grate area of 144 sq. ft., placed at the bottom of the upcast shaft, and assisted by the furnaces of six steam boilers.
The principal workings are 2 to 3 miles from the bottom of the shafts, the farthest being 3 miles. The haulage is done by three stationary engines, more than 20 miles of steel wire-rope being in daily use. Electric bells are employed for signalling on the engine planes.
All the coal is drawn to bank from the level of the Hutton seam by two vertical low-pressure engines, of 180 and 200 nominal H.P. respectively. The flat steel wire-ropes are 51 in. wide by 5 in. thick, weighing 36 lbs. per fathom. The cages are of steel: each weighs 35 cwt., and brings up at one time eight tubs of coal, each tub weighing when full 131 cwt., while the cage chains weigh 5 cwt. Hence the greatest weight on the rope at the moment of lifting from the bottom is 12 tons 31 cwt. Each engine when fully employed can raise 90 tons of coal per hour.
Sunderland Docks
SUNDERLAND DOCKS
Sunderland Docks
Sunderland is one of the largest coal-shipping and shipbuilding ports in the kingdom, and has now dock accommodation commensurate with this importance. At the mouth of the river Wear on its north bank is the Wearmouth Dock, belonging to the North Eastern Railway, and containing 6 acres of water area, with 201 ft. depth of high water over the cill at spring tides, and 17 ft. at neaps. On the south bank, and extending more than a mile along the seashore, are the three South Docks, belonging to the River Wear Commissioners; these all communicate, and contain together 44 acres of water area.
They have recently been provided with a sea lock, designed and carried out under the superintendence of the Engineer to the Commissioners, Mr. Henry H. Wake. This lock is 480 ft. long and 90 ft. wide, with 65 ft. width at the gates. The depth over the outer cill is 27 ft. and 231 ft., and that over the inner cill is 251 ft. and 22 ft., at high water of springs and neaps respectively; and as the depth in the channel outside is about the same, much of the traffic can be worked independently of the tide. The swing bridge, the dock gates, and the sluices are all worked by hydraulic machinery. In the chain cable and anchor testing works of the River Wear Commissioners, which are of the most complete kind, the testing operations are all effected by hydraulic power from an accumulator, at a pressure of 2000 lbs. per sq. in.
The quays are furnished with hydraulic and steam cranes and other appliances; and with extensive warehouse accommodation. At the docks and in the river are coal staiths, at which is shipped nearly the whole output from numerous large collieries in the county of Durham. In the harbour, submarine rock-boring and blasting operations by means of the diamond-drill apparatus are in progress. The limits of the port extend for six miles along the coast, and up the river Wear to Biddick Ford, about eight miles from the sea.
Langley Barony Tin Mines
LANGLEY BARONY LEAD MINES
Langley Barony Tin Mines
In the excursion to Langley Barony Lead Mines, the party travelled on the Newcastle and Carlisle Railway, by special train, to Haydon Bridge Station, passing the numerous collieries and iron works at Blaydon, Newborn, Wylam, &c., and also the Fourstones colliery and lime kilns, where coal is raised from the mountain limestone formation. A lower stratum of rock at the same place yields the Prudham building stone, used for the Army and Navy Hotel, Victoria Street, Westminster, and elsewhere.
At Haydon Bridge the party were received by Mr. T. J. Bewick, and were then taken in carriages to the mines. They first visited the Honeycrook adit and works, and afterwards the Leadbitter shaft and Joicey shaft, with the works adjoining. They then returned by another route to Hayden Bridge, where they were entertained at luncheon by Messrs. Bewick and Partners; and afterwards travelled back to Newcastle by special train.
The following description of the mines and works is supplied by the kindness of Mr. T. J. Bewick, M. Inst. M. E.
The Honeycrook adit, commenced in July 1871, is driven nearly due north in a "cross" vein, or one running north and south, for a distance of 82 fathoms. Here Bewick vein is intersected, and it is in this that the lead ore is met with. This vein dislocates the strata at this point, forming a fault of 51 fathoms throw, which increases eastwards until at Joicey shaft it is 7.1- fathoms, the north side being thrown down. Its underlay, or "bade," is slightly to the north, and the average bearing is about 67° east of north, magnetic. There is a thick covering of clay on the surface, and the existence of this vein was unknown until September 1872; since that time it has been driven upon for nearly 700 fathoms, or over three-quarters of a and worked at one point to a depth of 41 fathoms below the adit. It has so far yielded between 15,000 and 16,000 tons of lead ore. At the Honeycrook works are dressing floors and various machines for separating the lead ore from the matrix, and from other valueless material, such as rock and clay, with which it is intermixed in the vein. The machinery comprises a steam hoist for lifting the stuff to the top of the crushing house, in which is a Blake stonebreaker and a crushing mill with one pair of rolls. Adjoining on one side are the boiler and a horizontal steam engine, and on the opposite side a complete set of jigging machinery. In a house close by are a smaller crushing mill, for further reducing the material, a stonebreaker, jigging machines, elevators, four round "huddles," and other appliances — all driven by a vertical boiler and engine. Just outside are a series of collecting pits and two more round huddles. About 50 yards lower down the valley are another set of collecting pits, and a round huddle driven by a small water-wheel. Close to the latter is a vertical boiler and a steam force-pump, for lifting the water, used in the before-mentioned works, (which now contains a little lead ore in a finely powdered state) through pipes to large settling pits situated 95 ft. higher up the hill. In these pits the mud, containing a small percentage of ore, subsides, and is afterwards removed by manual labour, or by a travelling pump, and passed over three circular huddles (Zennor's) for the purpose of separating the ore from the waste. These huddles, and the machinery in connection therewith, are driven by a water-wheel.
On the hillside, above and north of the Honeycrook works, are the Leadbitter shaft, and the dressing and other machinery in connection therewith. This shaft is 70 fathoms in depth, the adit being 261 fathoms from the top; while below are the 11 fathoms, 27 fathoms, and 41 fathoms levels.
The first house reached, after leaving the Honeycrook works, contains a chat or small crushing mill, jigging machinery, and two round huddles, all driven by a horizontal engine by Bobey and Co., supplied with steam from a vertical boiler. Just above, and nearer Leadbitter shaft, is a house containing a crushing mill, set of jigging machinery, and other appliances, with a horizontal engine for working the same. At the shaft are three boilers for supplying steam to a double-cylinder winding engine, to one of Davey's single-cylinder non-condensing pumping engines, to a small oscillating engine working a lathe, to a Tangye engine for driving the saw-mill, and lastly to the engine before-mentioned in the crushing-mill home.
Near to Leadbitter shaft are two reservoirs, into which the water required for dressing the ores is collected. The large one is fed by a water race over three-quarters of a mile in length, and the small one by the water pumped from the mine.
About 700 yards to the north-east of Leadbitter shaft is the Joicey shaft, with dressing and other works. This shaft is nearly 41 fathoms in depth, and as yet the only communications between it and the workings are the edit and the 11 fathoms level—the former nearly 27 fathoms, and the latter 40 fathoms from the top.
The dressing floors are first reached. The machinery here is all under one roof; and consists of a boiler, a pair of horizontal engines, a Blake stonebreaker, large crushing mill, chat or small crushing mill, a complete set of jiggers, and other appliances. The necessary buddies for dressing the sludge and slime are not yet erected at this place. At the shaft top are two boilers, which at present supply steam to a pair of winding engines only, but are designed to be connected with one of Davey's compound pumping engines, and to engines driving a saw-mill and workshop, which it is proposed to erect at this place.
About half a mile to the north of Joicey shaft is a reservoir for impounding the drainage water of the district, from which it is conveyed in an open race to a small service dam. Close to the dressing works and near the shaft is another reservoir, into which, when necessary, the water will be pumped from the mine. A little south of the Joicey works is a storage reservoir, into which flows all the water used thereat; and from thence it runs by a water course to the Honeycrook dressing floors.
The system of "Dressing" the Lead Ore, or separating it from the gangue, and the rock and earth with which it occurs in the vein, is first to pass it through a stonebreaker or a pair of crushing rollers—not unfrequently indeed through both; from which, in its reduced state, it is carried through a series of inclined revolving cylinders or " trommels," each perforated with holes of different sizes. Through these holes the oro falls into the " jiggers " or sieves, which are similarly perforated. These sieves are themselves fixed, but the water in which they are placed is moved up and down by largo square pistons, worked by eccentrics. According to circumstances, there are two, three, or four of these sieves placed in succession, each a little lower than the preceding one; and thus the crushed material, by the admixture and motion of the water, is carried slowly forward, the lead ore and other heavy minerals settling on the sieve, or if small enough falling through the holes into the tub beneath; from which it is occasionally taken off by a valve in the bottom. The light rock or "waste" is carried over the end of the lowest sieve, and removed by wagon or barrow to the "dead" heap. Much of the material collected on the sieves, and in the tub below, is a mixture, in a more or less united form, of oro and valueless mineral (in this case mostly sulphate of baryta), or of ore and rock. When in this condition it is further reduced, by being again crushed in a smaller mill, in which the rolls are set nearer together. A considerable proportion is here crushed very small, and carried by the water into tanks or "classifiers"; from which it is taken to similar jiggers, perforated with smaller holes, and where the pistons have a shorter stroke and a higher speed.
Some of the ore taken from the tubs has a slight admixture of sand, and has to be passed under the "propeller" or "knife huddle." This is a cylindrical framework of iron, revolving on a horizontal axis, and carrying a series of scrapers or knife blades, fixed in spiral lines round the outside. These revolve close to a bed or channel, hollowed to the same radius; and, the ore being supplied at one end of the bed, the revolving blades not only cause it to travel forward, but also sweep it continually upwards on the curved bed against a stream of clean water flowing across it. The water separates and carries off the sand, leaving the ore almost pure by the time it arrives at the further end of the bed, from which it falls into a receptacle.
Thus the material, on being first brought out of the mine, is reduced in size and then passed through the jiggers until most of the ore is extracted. There is however still a little left, known as "slimes." These slimes are run on to the apex of a conical huddle, 16 to 20 ft. diameter, and being here mixed with an additional quantity of water (clean if practicable), flow down the slope of the cone. The ore and the heaviest of the minerals subside first, near the apex: the lighter portions go towards the periphery and settle there, or are carried away in the water. These huddles fill with deposit to the depth of a foot or thereabouts, and are then emptied by manual labour. The outer portion is thrown away, as containing no ore; the middle and upper portions are again passed over these huddles, as often as necessary, until the lead ore is nearly pure enough to send to market.
The final operation with this class of ore is to "dolly" it, that is to put the ore into an ordinary large sized cylindrical wooden tub with water, agitate it so that the whole is thoroughly intermixed, and then rapidly strike the sides of the tub with heavy pieces of wood or iron bars; in some instances this is done by hammers driven by machinery, but at these mines boys are employed in this operation. This has the effect of causing the ore to settle at the bottom or lower part of the tub, and the lighter sand or waste to come to the top. The ore is taken out of the tub by manual labour, and is now fit for market.
All the water used in the manipulation of the ore, as before described, is run into a series of pits 20 to 30 ft. long, about 3 ft. wide and 2 ft. deep; and here the bulk of the remaining mud, containing a small proportion of finely powdered lead ore, settles. When these pits become full, the mud is removed and passed, as just described, over round buddies and through the dolly tub, until practically all the ore is saved.
See Also
Sources of Information