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September, 1938

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The problem of mine drainage has always exercised the ingenuity of the miner as soon as vein deposits have been followed below the ground water level, or "water table," when any excavations made will sooner or later fill with water. In mountainous country this may not occur until a comparatively late stage of development, as the water table may be a considerable distance below surface level, but there are indeed very few areas where it will not some time become a matter of vital importance. In the 16th century, the metalliferous mines that Agricola visited and described were many of them already troubled with water, and a considerable section of his book De Re Metallica is devoted to pumps and water raising mechanisms. In this country the question of water troubles did not reach an acute stage in the lead mines until nearly a century later, when some of the mines of Central and North Wales were being hampered in their development by accumulating water. The case of the mines in all the coalfields, and the deeper tin and copper mines of Cornwall, showed that water troubles were already great in the 17th century. Drainage had been mainly achieved by means of simple bucket lifts, using either an endless chain of buckets or straightforward haulage in buckets up the shaft. For these methods, horse gins were mainly used as motive power, though in favourable localities water wheels were harnessed for driving the pumps. At the best these methods could do little more than keep the water in check during working times, and in fairly restricted working spaces.

When Plot was writing his "History of Staffordshire" in 1686, he referred to the trouble then being experienced from flooding of the mines and says of drainage, "The ordinary ways they use are by sough or gin. The former when they have the advantage of fall of ground enough but when they have no fall they draw it up by gin. The gin is turned by men or horses, using barrels."

At the end of the 17th century the first attempts were made to apply the power of steam to this task. Savery in 1698 patented, "A new invention for raising water and occasioning motion to all sorts of mill work by the impellent force of fire, which will be of great use and advantage for drayning mines, serveing houses with water, and for the working of all sorts of mills where they have not benefitt of water nor constant windes." In 1702 Savery gave an account of his patent in a famous booklet "The Miners Friend; or an engine to raise water by fire, described, and the manner of fixing it in mines, with an account of the several uses it is applicable unto ; and an answer to the objections made against it, by Thos. Savery, Gent, London, 1702." His patent was granted for a period of 14 years, and in 1699 this period was extended for a further 21 years, i.e., until 1733. It was under this general patent that most of the early steam engines were made, although they were entirely different in construction. The essence of Savery's engine was the creation of a vacuum in a steam cylinder, by filling the cylinder with steam, closing all valves and injecting cold water to produce condensation, thus producing the vacuum; the cylinder was then opened to the. rising pipe from the mine sump, when atmospheric pressure forced the water up into the cylinder. The rising main was then shut off, an escape pipe opened, and steam turned on to force the water out of the cylinder and up the delivery pipe. In principle this engine was like the modern pulsometer pump, with no moving parts except the water column and the valves. Savery expected the "engine" to suck water up to 26 ft., and force it up to 80 ft. in the delivery pipe, thus getting approximately a 100 ft. lift. By means of repeated stages the deepest mines could thus be pumped. Savery's engines were installed at a few mines but from a variety of causes they were never very successful.

A few years later, Thomas Newcomen made a steam engine incorporating the essentials of moving piston giving a reciprocating motion to a rocking beam. This was ideally suited to pumping work, as the pump spears could be carried directly down the shaft from one end of the engine beam. Motion was obtained by a careful balance of parts so that with a slight steam pressure (about 5 lb. per sq. in.) under the piston, the pump rods sunk to the bottom of their stroke, with the piston at top of the cylinder. The steam was condensed by injection of cold water, and the atmospheric pressure on the piston with partial vacuum below it gave sufficient force to lift the pump rods and the column of water in the rising main. The first engine of this type was erected in 1712 at a colliery near Dudley and proved a success, though fuel consumption was very high. A Newcomen engine was soon after at work on Wheal Vor tin mine, Cornwall, and others in most of the coal fields. The engine was vastly popular in the collieries, but in the metalliferous mining areas the high fuel consumption made the running very costly. An engine, supplied in 1726 to the York Buildings Company Water Works, London, was, in 1732, sold to the London Lead Company for re-erection at their lead mines in Halkyn, North Wales; it is reported to have cost £1,000 a year in fuel. Not many Newcomen engines were used in lead mining largely because of the very high running costs in areas at any distance from a coal field.

The commonest arrangement of the steam engine was to place it at the surface with spears down a main shaft working direct lift pumps. The stroke of the early engines was from 6 to 10 ft., the cylinder diameter generally about 33 to 50 in., and the pump barrel 10 or 12 in. An estimate of 1731 gives "The Bore of Pumps that will Discharge 400 hogsheads in One Hour must be 13 inches Diameter also the Diameter of the Cylinder 33 Inches to run 12 Strakes p minute ye Strakes 6 foot long." The lift was 22 fathoms, and the total cost of the engine and pumps £849 16s. 0d. The cost of "keeping" it in fuel, after a long run, was given as £4 per week. This agrees with general figures of £4 to £5 per week averaged over 30 engines on the Newcastle coal field between 1720 and 1750, where coal was on the spot and very cheap. At long distances from the coal field, the cost was more than doubled. In 1750, coal for an engine at Middleton Tyas copper mine was quoted at approximately 11s. per ton, and the engineers found it cheaper to build a battery of pumps worked by horses. The cost of horses would be about the same everywhere, and their performance is given as follows :—

"40 Fathom shaft, 2 Horses to Work 3 Hours for a shift will Draw 35 Tubbs of water in an hour each Tubb Containing 80 Gallons — in 24 Hours 67200 Gallons 8 Shifts of Horses 2 in each Shift including Driver will Deserve 3sh per shift which in 24 Hours is 24 sh. and does not draw 1/3 the quantity which a Fire Engine does."

Although the Newcomen engine was popular in the coal fields, few areas except Cornwall favoured it for metalliferous mines. The topography of Cornwall was such that it was almost impossible to construct deep drainage adits, as many of the mines were •not much above sea level. Cornwall became one of the busiest scenes of Boulton and Watts' activities when their improved engine was put on the market, as it saved enormously on the fuel costs.

As early as 1704 the mines of Trelogan and Pant-y-Pwl, near Halkyn, North Wales, were reported as being seriously hampered by water, and incapable of being continued unless the water could be got away. The lessees of these mines, the London Lead Company, planned to drive up a level from the lower slopes of the hills to drain away the accumulating water in their veins, and commenced what later became the first Halkyn Tunnel. In their inexperience this level was planned to cut the vein at about the bottom level then worked, and thus was being made simply as a drain to the existing workings. In 1721 the whole scheme was reviewed and after a survey of the ground a second level was commenced which, on reaching the Trelogan veins, would have gained a depth of 40 yd. below the "sole" of the mine as then worked; it was expected it would thus unwater sufficient ground for many years' extended workings. The progress of this level was very slow due to the hard rock encountered, and for many years before its completion the mines were drowned out. In 1728 a survey of Llanfrothen mines, Merioneth, was made and a level planned that, with a length of 340 yd., would gain 50 yd. in depth. This was driven and proved highly advantageous. In the meantime to relieve Trelogan mine, a "Fire Engine" (Newcomen steam engine) was ordered and put at work in September, 1731, £105 being paid in licence to use it. In 1732 the York Buildings engine was added to it, and between them the mines were unwatered and kept open until the deep drainage level was completed. The final cost of the level worked out at no more than the running cost of the engines, with the vastly different result that expenditure ceased on completion of the level but with the engines would have been a continuing charge as long as the mine worked.

Between 1720 and 1735 the London Lead Company had a very wide experience of the cost and advantages of levels as compared with engine drainage in their mining fields in the North of England and several parts of Scotland and Ireland, which confirmed them in their policy of planning large scale deep levels wherever possible. In Derbyshire they took up leases in the area around Mill Close mine, in the parishes of Winster, Birchover, and Wensley, only to find the old workings on their veins drowned out, "many veins were seen which cannot be examined for water, so think it advisable to drive a sough from 200 yards below our shaft on Delph vein and use several old shafts for ventilation; we shall gain 44 yards depth at a cost of £100." A larger sough was started in 1722, and by the end of 1723 had progressed 100 fathoms and had cut 10 veins. In 1744 this sough — the Yatestoop sough — cut the Mill Close vein and was later carried to the Watering Close vein complex. A nearly parallel level, the Cowley Sough, 2,800 yd. in length, was started in 1743, and the two together finally unwatered most of the Wensley and Birchover ground. The total cost of the two levels was over £50,000, but the London Lead Company considered themselves more than repaid by the fresh ground won by their means. At Mill Close mine the sough was not deep enough to allow very great development so, in 1748, a deep shaft was sunk alongside the sough and a Newcomen engine (supplied by Darby of Coalbrookdale) was installed there to lift water to the sough level. Other sumps were made on the vein and connected with the engine by sliding rods and bell crank levers. On the whole it proved to be a fairly successful job, but the engine running cost soon became almost prohibitive, due to the price of fuel and difficulty of transport which was mainly by pack horse train. The engine was sold in 1764. After this experience the London Lead Company made no further use of the steam engine but trusted everywhere to deep levels.

In Derbyshire the success of the Yatestoop sough inspired others in many parts of the area, but few of them had the same happy results. Farey writing in 1811 says "it may be right however, here to mention, that most of these soughs have proved unprofitable speculations, owing to the tedious time they were in driving, the Miners in the meantime continuing their exertions by pumping and short soughs, much of the ore was got before the great soughs began to act, but more owing to the mines, particularly in the lower Lime rocks, growing poorer as they descended, and ceasing entirely to carry ore in many situations where the highest expectations were entertained by the Miners and Soughers." Except at Mill Close, very little mining has been done in Derbyshire below the level of the great soughs.

During the driving of the earlier soughs it was realised that apart from acting as a direct drain to a particular mine, the sough to some extent unwatered the ground in a broad flattish V above its whole length. In many cases it tapped large feeders of water that otherwise would have found their way into the mine workings. A sough therefore may confer benefits on many mine leases other than the one for which it was first designed. For this reason, about 1740, it became the customary practice to drive a sough by a partnership of all the mine proprietors likely to benefit. This very reasonable arrangement, however, led to many difficulties in practice. Small or struggling mines, that might be improved in five or ten years time when the sough reached them, were often unable to weather the intervening period and maintain their proportionate payment. When the drive was particularly long or slow, veins at the far end had often been followed to such depth during the driving of the sough, that by the time it was completed, they were nearly down to sough level, and so were little better for it. For these and similar reasons, the great soughs were mainly the work of the large proprietors who had sufficient capital and enough spread of leases to carry the steady expense of driving, for ten, twenty, or thirty years, as a normal development charge, and yet be ready and virile enough to take full advantage when completed.

Permission or wayleave to drive a sough was occasionally let or sold to a partnership of adventurers who counted on the proportions from all mines being worked to make their project a paying proposition. A notice of about 1760 illuminates many of these points.

In the areas like Wharfedale (Yorkshire), Alston Moor (Cumberland), or the Allendales (Northumberland), where all or most of the mines were in the hands of a single proprietor or lessee, the longest drainage levels were driven about the end of the 18th and during the 19th centuries. Nent Force level at Alston is an example of this type of undertaking. The mineral ground of Alston Moor was mainly in the hands of the Commissioners of Greenwich Hospital, and a considerable area of the Nent valley and Nenthead were leased to the London Lead Company. After considerable discussions and surveys the Greenwich Hospital decided to cut a drainage level from the bed of the river Nent at Alston, south-east to Nenthead about 5 miles, to unwater their principal mining grounds. The level was laid out by Smeaton who was then one of the receivers of the Hospital, and was commenced in 1773. It was driven at a dead level as far as Lovelady Shield, some 3¾ miles, so that a depth of about 4 ft. of water can be maintained in it, making it serviceable as a boat level. At Lovelady Shield there was a rise of 35 fathoms ; the level was then carried forward into the Nenthead ground. A large number of new veins were expected to be discovered in driving it, but the results in that respect were disappointing, although over 7,000 bings of ore were got from the veins and strings cut. The level is still of great value and efficiency in draining the mines along its length. The planned dimensions were 9 by 9 ft., but in much of the softer ground this was increased to 9 by 16 ft. Driving occupied 60 years and cost £80,000. Boats, 30 ft. long, were frequently used in it, but mainly for visiting tourists.

Many similar levels were planned and carried out on a rather smaller scale in the latter part of the 18th century. At Great Punchard Gill, in North Yorkshire, a long level was driven with such slight fall that the partial walling of the mouth converted it into a boat level, by which much of the ore from the mines was conveyed to surface, on shallow-draft rafts or small boats. A similar level with double purpose was driven to unwater the Hebden Moor ground in Wharfedale, and there too, boats were used for drawing ore. Among the larger schemes, the Duke's level at Grassington, Wharfedale, over three miles long, took 33 years in the driving, at a cost of over £30,000. The Blackett level in Allendale was planned by Sopwith to run from Allendale Town to Allenheads, a distance of 7 miles. It was commenced in 1859 and by 1912 completed as far as Sparty Lee, 4½ miles at an estimated cost of £250,000. Its gradient is 9 ft. per mile, and its section 7 by 4 ft. In North Wales, the 19th century saw the several Halkyn Tunnel schemes, some of the later of which have been extended in the 20th century, and are not yet completed.

From abundant evidence, on only a fraction of which this review is based, it seems that the steam engine had a very brief period of use in lead mining, but was completely displaced by 1760 by the deep drainage level, which still holds its own in many areas. The drainage level is a tedious and costly undertaking, but once made is a permanent asset, while any means of power pumping imposes a constant running charge, and is of value only so long as it continues to run. It is possible for a temporary stoppage in a pumping plant, to lead to a permanent drowning out that may leave the mine almost beyond hope of recovery. An example of this is seen in the Sir Francis (Denys) level, in Swaledale. This was driven early in the 19th century, from a low point on the west side of Gunnerside Beck, to intersect and drain the Friarfold Vein, at a distance of about a mile. At the inner end an engine room was cut, and a shaft sunk from the surface. A sump was put down 40 fathoms to reach the Hardraw Scar Limestone, and the sump drained by a hydraulic pumping engine built at the main level end. The shaft, level, and engine cost £13,000 above the value of the ore obtained in cutting. After a very few years working, a mishap to the pump gear at the bottom of the sump caused the shaft to flood; the mishap was such that the gear could not be withdrawn, and the whole mine was lost. Very little greater outlay would have brought up a deeper level at sump bottom, and the mines would probably still have been open.

If a long life is planned for a mine, then deep drainage levels are the most favoured method of unwatering. Mechanical pumping quickly became out of date during the first century of development of the steam engine, when outputs were small and development and gigantic output methods have altered all the conditions that the 18th century miner had to face.

Drawings and Photographs accompanying the article