The Surveyor’s Job At A Coal Mine
The mark painted on the last arch at the tailgate ripping lip denoted that that the centre of the arch was off line by 50 centimetres (half a metre).
‘That’s it then’, said the Gate-end Deputy, ‘the line’s off centre again’. This was usually the case. Generally neither the Deputy or the workmen or even the Undermanager could see that the statement just made, was in reverse.
The centre of the arch was off line by 50 centimetres compared to the line put on by the surveyors, but to them the only thing that the Surveyor and his assistants and linesmen had done that day was to make the gate off line by putting the centre line in the wrong place, and having done so would now make their way out of the pit and their day’s job was at an end!
That mark was probably the last thing that the Surveyor would be thinking about and it certainly would not be the end of the day’s work! Most miners only saw surveyors at the gate end ripping lip putting on a white line and thought that was all there was to it!
No one ever mentioned that the gate may have wandered off line during the last day or so, due to panzer creep or even bad alignment… No one ever thought that the gate ought to follow the bearing put on by the Surveyor or linesmen….. only a small amount of deviation from the planned bearing can be allowed as safety needs to be borne in mind, particularly if the gate is running ‘parallel’ to an old gate.
Maybe an insight into surveying and the job of the Surveyor will explain many factors that remain a mystery for the majority of people.
The origin of the bearing set out when the gate road started, and the mark made on the last arch set were way back in the complexity of calculations, and probably many years of previous surveys to arrive at the line of marks, depending on the age of the seam workings or the age of the colliery.
The bearing would have been set out from a base line in settled ground (strata) in a gate road outbye, which would have been surveyed to and checked from the pit bottom base line in the past, and ultimately the bearing and position would have originated at the surface from triangulation stations set out by the Ordnance Survey and brought in to the colliery surface base by means of intersection or resection methods and then transferred underground by correlation surveys.
The bearing of the pin lines set up by the Surveyor underground would of course occasionally have to be adjusted, to take into consideration movement of the strata, which is always present in the mine, particularly close to the coal face where the extraction of the coal and gate ripping allows the immediate ground to subside. Sometimes this subsidence is also accompanied by side thrust and floor heave. Most people in a mining area have seen evidence of coal mining subsidence at the surface in the form of cracks in buildings, water mains broken and sometimes slumping or fissures in roads, etc. The subsidence has to start somewhere, and that somewhere is at the coalface.
Surveying is a type of exact science, within limits of error, which are usually and hopefully compensating. Invariably calculations are involved. Surface surveying is seen by the majority of the public in the form of motorways, with their gentle curves and gradients, various bridge layouts and complicated crossovers, such as Spaghetti Junction (Gravelley Hill interchange on the M6) or in the form of new housing estate layouts or drainage systems for surface water or sewers.
Underground surveying in mines is done on the same lines but of course it is in the dark, and one cannot see to do survey work without the aid of artificial light, (cap lamp), but other factors influence and hinder the work more, such as dust, heat, damp or wet conditions, strong air currents, low conditions or steep gradients, and places where men and transport regularly pass in fairly narrow places. In the past of course ponies as well were a problem.
Other factors which greatly influence the accuracy of underground work compared with surface work are mentioned later.
The art of surveying has been practised for many thousands of years to pinpoint position. The Babylonians and the Chinese used the stars to orientate their position on the Earth.
The Arabs used mathematics such as algebra to assist them in their building.
A holing through of a water course driven straight from both ends beneath a mountain on the island of Samos during the years 540-523 BC proved that survey methods were used, albeit that the error was quite substantial, being about 9m out in alignment and 3m out in level, a connection having to be made at right angles after the headings had passed one another.
The ancient Egyptians used surveying techniques with the aid of trigonometry and geometry to build the pyramids at Giza near Cairo thousands of years ago.
Gold mine plans exist on fragments of papyrus dating from 1300 BC. These plans must have been prepared and plotted from measurements and directions taken. Prior to this, crude sketches had been drawn on the walls of an ancient copper mine in the Sinai Mountains and are dated to 4,000 BC.
The Etruscans and the Greeks left the Romans with knowledge of the principles of surveying, and remnants of surveying instruments used by the Romans have been found in archeological excavations.
The Romans are best remembered in Britain for the straightness of their roads and the fortifications and the occasional villa or aqueduct throughout the country and the defence walls and ditches built in the north named Hadrian’s and Antonine, to keep out the Picts and Scots.
Instruments were used to maintain the direction of the roads, one of which was called the groma. The instrument was basically a pole with a wooden cross at right angles at the top, and there was a string hanging down from each of the four ends, each weighted down by a plumb-bob. This enabled a person to hold the pole firmly on the ground or stand, and sight through two of the string lines in the direction desired, firstly backwards along the roadway made, then forwards to mark out a point in front for the roadway to be made, along the level or uphill and down dale, or even at right angles, left or right.
Another instrument called a dioptra was also used. This instrument was so divided in direction that any angle, other than right angles could be set out or lined in.
The Romans used triangles in their work to set out and measure land areas of uneven shapes, and also to find distances across rivers or gorges etc which were inaccessible for measuring, (using trigonometry and geometry). Ancient mathematicians left us with theorems, eg, Pythagoras. He is probably remembered for the most famous theorem, as he proved that the square of the hypotenuse of a triangle was equal to the sum of the squares on the opposite two sides.
Euclid was another scholar, and many mathematical formulae were developed from these ancient times.
No written records have been found to date of survey work done by the Romans. However it is known that they mined coal because stores of coal or ashes and cinders have been found at numerous sites throughout the country, particularly fortifications. At Housesteads, a fortification on Hadrian’s Wall in the North East there is evidence of the underfloor hot air heating system that was used and fired by coal. Coal seams are close to the surface or outcrop nearby and mining continued in that area into the first 2 or 3 years of the 21st Century.
The Roman road Watling Street passes right through part of the Midlands coalfield where coal outcrops at the surface. Rykneld Street now part of the A60 passes through the western edge of the Nottinghamshire & Derbyshire Coalfield. The Romans also mined lead and fluorspar in Derbyshire. After the Roman legions left Britain in 410 AD, little is known of coal mining, until the Monks recorded leases for the mining of coal in the Middle Ages. In the Domesday Survey of Britain carried out in the years 1086-1089, there is no mention of coal or coal mining, although it is thought that mining was being done, albeit on a small scale. Possibly when the survey was done, I would imagine in the summer months mining would not have been taking place as the men would probably have been ‘farming’ for the Lord of the Manor and in the winter the coal would have been ‘farmed’. Valuable minerals such as gold, silver, copper, lead, tin etc were mentioned in many parts of the country. Coal is a ‘rock’ not a mineral and is laid down among sedimentary strata. Wood was the chief form of heating at that time. However in 1102 it is recorded that coal mining began in the Manor of Caerphilly, at Llanvabon.
In the 1200s, numerous mentions of coal diggings are recorded. The first local areas of coal mining were at Denby, Breaston and Wingerworth, in Derbyshire in 1285. Sometimes the coal was worked alongside the iron ore or fireclay. Coal was also mined near Wollaton and Cossall in Nottinghamshire. Diggings were also recorded in South Derbyshire / Leicestershire.
Mining at Selston, Alfreton and Smotherfly in Derbyshire began in the early 1300s and mining at Wollaton began in the 1400s. In the late 1500s it is noted that miners in Nottinghamshire were paid 6d to 7d a day. Mining locally in the Parish of Sutton-in-Ashfield at Hucknall under Huthwaite was begun in 1584, although mining had been practised for many years in neighbouring Blackwell Parish.
However none of these workings had been put on a plan. Old shafts, or dirt heaps that contained small pieces of coal have been found denoting that mining had taken place. Many shafts and Bell pits were located from aerial photographs. Some old shafts were only known about when they collapsed. Many old shafts upon abandonment were just covered over with wood etc and spoil heaped on top. Another method was to place wooden baulks across the shafts about 10 yards down and then fill the shaft with rubble up to ground level. Many shafts have been found by noting that nettles, dock leaves and other acid loving plants were growing in small circular clusters. Numerous shaft collapses have occurred in recent years as the wooden baulks had rotted verifying my observations.
As the overburden increased from the early days of outcropping or ‘farming’ the coal, a shallow shaft of small diameter was sunk and the coal around the base of it excavated as far as possible until the roof began to collapse and then it was abandoned and another shaft sunk nearby and the debris from this was tipped into the old abandoned shaft. These were called ‘Bell pits’ or ‘Beehive pits’ from the shape that they created. Generally they were not more than 20 feet (6m) deep and about 5 feet (1.5m) diameter.
Many old shafts have been searched for but not found. Many others have only been located when the area has been Opencasted since the start of that system as a War Effort in 1942. All the known or surmised position of shafts in the Midlands region have been surveyed / measured and recorded and are kept in the Mining Records Office (presently located at the Coal Authority, Mansfield, Notts). The information has been collated from a variety of sources:- a local Surveyor, James Ashton Twigg of Chesterfield, and Peter Perez Burdett produced many excellent plans of the surface districts of Derbyshire and bordering Nottinghamshire around 1820-1836 for the major land owners. In the early 1830s another Surveyor called George Sanderson produced a very detailed plan of all surface lands within 20 miles of Mansfield. Positions of mine shafts are shown on these plans. John Farey produced a book in 1811 on the geology of Derbyshire and listed the position of all the coal mines working and many others that had recently closed; First edition Ordnance Survey plans were produced from 1875-1881; Six Inch plans were introduced in 1888; Geological plans 1900-1920; Other Local Surveyor’s plans; various Colliery Company plans, etc.
It is known that some 11,000+ old shafts exist in Lancashire, some 7,000 or 8,000 in Yorkshire and approx 8,000 and around 1,100 adits in Derbyshire and Nottinghamshire and Leicestershire. As stated, many shafts have never been found to date, although are thought to exist. Some still keep being found on new housing developments.
Plans of coal workings were prepared in the 1600s by Surveyors or Viewers and rough areas of extraction shown, but no specific details were delineated.
As more and more mining took place in the 1700s, further distances from the pit bottom or shaft eye were excavated and wooden supports were set to hold up the roof, and it sometimes became necessary to sink further shafts to aid ventilation, as generally no artificial ventilation aids were available at the time. Because these mines were still relatively shallow, it was generally easy to see on the surface where mining had taken place due to the subsidence of the land, and they would sink a shaft in the ground just behind or in front of the working. These shafts were sometimes sunk to facilitate easier handling of the coal, so that they would not have to transport it so far in the very low conditions that used to prevail and the old shaft would probably be abandoned.
The leases granted to work the coal were granted by the landowner and so the boundary of that lease could be seen on the surface in the form of a hedge, a footpath, road or a stream etc.
When surveys of the mine workings began to be carried out underground, they would repeat the survey afterwards on the surface and peg out the route, so they could see where they had been underground. It became important to know whether or not a mine working had extended into someone else’s lease area. These surveys would have been quite crude compared with today’s standards, and the use of a free swinging magnetic needle would have been needed to orientate the direction of the roadway underground with the position being relevant to the shaft bottom. Using this method there was no need to keep a record of the survey or to plot the results on a plan. The method of ‘pegging out’ at the surface was still being described in a Colliery Management book in 1876, although by then it was necessary to keep mine plans by law, and had been since 1850!
A modified mariners’ compass had been used in the copper mines of Tuscany in the 1400s to carry out surveys of the workings.
A bubble level was designed in about 1660 using water in sealed tubes, (the Romans were using a horizontal tube about 6 feet (1.83m) long and sighting along the surface of the water), but it was not until around 1750 that a smaller and more convenient bubble was used underground, in conjunction with a plumb bob and straight edge about 7’6” (2.29m) long to determine differences in height between one point and another. In fact this system was still being used on very steep gradients in some local pits until the 1940s in preference to levelling instruments, possibly due to the inability to focus at very short range at that time!
The first Treatise in Britain book, devoted to mine surveying, was by Thomas Houghton in 1681.
The introduction of a dial into the Cornish tin mines for surveying purposes towards the end of the 1700s was an adaption of the dial used for land surveying.
Plans kept in the early 1800s were mainly for royalty purposes, i.e. for the payment to owners of the land under which the coal had been mined. Plans showing Copyhold areas were also kept. This is where the mineral owner had a ‘copy’ of the Lord of the Manor’s scroll where the mineral rights had been severed from the surface.
Survey methods differed greatly, and sometimes an Agent for the owner would carry out a check or verification survey, to verify the area being worked. The National Coal Board did this after 1947 on occasion with their licenced mines where private surveyors did the routine work. However if the royalty was based on the tonnage extracted only, and not on the area extracted as well, some mine owners deemed that surveys were not necessary and would not pay for one. Safety was a factor that was hardly ever considered!
Thomas Sopwith, Surveyor of mines among other things, invented the well known levelling staff or stave. When in the Forest of Dean, which is an ancient mining area, he found that not one single plan existed of any of the coal workings there. In 1833 he surveyed all the accessible mines and in one particular adit that had been driven for a water-course over a number of years, actually found that the heading was going in almost the opposite direction to what it had originally been set out at! Obviously danger lurked in all parts.
The Cornish surveyors in the tin and copper mines were the first in Britain around 1797 to apply the ‘fast needle’ system of traversing underground, by the introduction of the vernier dial or circumferenter. This method used the fixed needle instead of a free-swinging one.
The theodolite had been invented by one Leonard Digges, a geometrician and an Elizabethan in 1571.
The telescope had been invented in 1608, and had first been applied to an instrument for measuring angles around 1700.
However these sophisticated instruments are not thought to have been used for the surveying of coal mines until much later, when John Budge, a mining engineer from the North East of England, was credited with introducing the theodolite underground in 1825. John Farey noted in 1811 that were some 60 odd mines at work in Nottinghamshire and Derbyshire.
There is a plan of some coal workings in Nottinghamshire, around the Nuttall area dating from the 1760s, which shows some detail of underground roadways and workings, and is assumed to have been made from measurements and bearings taken.