The colliery was in the Aber Valley about 12 miles N.N.W. of Cardiff. There were two shafts, each 535 yards deep and 18 feet 6 inches in diameter, sunk to the Steam Coal Seams of the South Wales Coalfield and equipped to deal with a large output. The operations to sink the shafts had begun about 1890 and coal had been worked since 1896. Until a few months before the disaster, Mr. William T. Rees, mining engineer of Aberdare, acted as agent for the owners, when ill health had compelled him to give up the position when Mr. Robert T. Rees was appointed agent and devoted much of his time there often living at the colliery. The certificated manager was Mr. Edward Shaw who succeeded his father on his death about 10 weeks prior to the explosion. Before his appointment he had acted as undermanager, overman and fireman and although only 30 years of age had a lot of mining experience. There was no undermanager, Mr. Shaw did the daily supervision under the Act but there was a day and a night overman. There were eight firemen divided equally between the two shifts.
The explosion occurred about 5.50 a.m. on the 12th. May after most of the night men had left the mine and before any of the day men had descended, except for the firemen who had gone down to inspect the working places before any of the colliers were allowed down to work. At the time, 450 men and boys were employed underground during the day and 240 at night. The colliery produced 6,200 tons per week. The coal came from the Four Feet Seam which was about 6 feet thick and the Six feet Seam, which was 3 feet 6 inches thick and 25 yards below the former seam. Both were fairly horizontal but undulated to some extent in some places. The field was also traversed by several faults which brought certain area of the upper seam nearly opposite the lower seam in certain areas at the faults. at the time, the workings in one seam did not overlap those of the other but in some districts, one seam was connected to the other by short headings driven through the intervening strata.
An area with a diameter of 500 yards, centred on one of the shafts had been left unworked to avoid movements of the ground through which the shafts were sunk and to prevent the buildings and engines at the surface form being affected by subsidence. As a result of these problems, the workings had become separated into a series of isolated districts labelled A to G. In each of these districts coal was worked.
The haulage was carried out by horses an all the level roads and haulage engines powered by compressed air were installed on all rising gradients and self- acting planes on the descending gradients on the east side of the winding pit. The gauge of the railway mine was 3 feet and the mine waggons weighed between eight and nine hundredweight empty and 37 cwt. when loaded. The end of the waggon was made of sheet iron and the other was open with two strong iron bars which were hinged and fitted with a pin and cotter to prevent large cobs of coal falling out. The result of piling coal high above the level of the sides and having an end that was open, was that coal was strewn along the haulage roads all the way from the face to the bottom of the winding shaft. This coal was continually being trampled and crushed by the hooves of t e horses and the feet of the men and a fine powder was produced throughout the haulage roads. This carried the explosion throughout the whole of the colliery.
Coal was worked in both seams by the longwall method and an essential feature of this method was the maintenance of a continuous space in which the colliers work all round the edge of the solid coal in the districts. The colliers won the coal from the face and loaded it into the waggons standing near the face. Each waggon stood at the inner end of a roadway or gallery 10 or 12 feet wide which was made through the pillars of debris which supported the roof in the space from which the coal had already been removed. The roof in the roadways was supported by timber where necessary. The roadways were 14 to 15 feet apart and most of them were at right angles to the face. They ended in an open space at the face at one end and in a cross heading, which was a branch of one of the main haulage ways on the other. The roof of the seam rested on solid coal at the face on one side and on the packing debris, built between the stall roads on the other. the solid coal made a good support for the roof but the debris put pressure on the roof and it was known, that at about 100 yards from the face, the debris had become so compressed, that it was about half its original bulk and completely solid and was found to have sunk to half the thickness of the seam. in the 100 yards from this region to the face, the roof was slowly sinking and the height of the stall roads gradually diminishing.
To preserve the height of the roadways in this zone, the roof was taken down and the resulting debris carried forward to fill the space behind the colliers with the space between the pack and the colliers maintained at a convenient width for the colliers to work. In seams of soft coal the roof can be got down with picks and wedges but where the roof is hard, blasting had to be carried out. This was the case at the Universal colliery.
The blasting operations consisted of boring a hole 2 to 4 feet by one and a quarter to one and half inches in diameter in the ground above or below the seam, charging it with explosive, tamping it firmly with clay or other material, and firing it by a fuse or an electric battery. As a rule the ground is broken by the explosion and the shothole destroyed but it occasionally happens that the tamping gives way resulting in blown out shot and the shot hole remains almost intact. On the day of the explosion, there were two night firemen in the pit and the four day firemen had descended. All six firemen were killed in the explosion. One of the firemen was Gwilym Jones who acted a shotfirer in the Pretoria district which was the only district in which shotfiring had been sanctioned by the management during the interval between the close of the night shift at 4 a.m. and the start of the day shift at
The ventilation was provided by a Walker fan, 24 feet in diameter. with the engine making 33 revolutions per minute, the total quantity of air circulating was about 120, 000 cubic feet per minute. The intake and the return airway passed through the pillar that had been left to protect the shaft to connect with the working’s. The air from the surface divided into two currents at the bottom of the downcast shaft, one went east and one west. Part of the return air from B district ventilated A district and the whole of the return air from D district ventilated E district. Each of the other districts, C, F and G were ventilated by it’s own current. There were five ventilating districts with the meaning of the Coal Mines Regulation Act, 1887. No.1 took in all the working on the east side of the shaft and the total quantity of air passing into this on the last measurement before the disaster was 39,900 cubic feet per minute. No.2 comprised all the working on the north side and was called ‘Ladysmith’ and had 11,200 cubic feet per minute. No3. was comprised of workings on the west in two separate areas named, ‘Kimberley’ and ‘Mafeking’ districts and through which 9,120 cubic feet of air wee passing. No.4 was called ‘Pretoria’ and had 9,900 cubic feet. No.3 consisted of the working on the extreme south-west called the Six feet of the No.2 South District through which passed 9,000 cubic feet. in addition to these districts there was a small area of discontinued Six feet workings ventilated by a split taken from the main west intake and joined the return from ‘Ladysmith.’ Air doors, consisting of a wooden door hinged to a wooden frame surrounded by a brick wall made an air tight between the frame and the roof and sides of the passage and were set in all roads necessary for the transport of coal between the intake and return airways. Brattice sheets were also hung in those passages in the workings thorough which only a limited quantity of air was intended to pass. At two pits where the return air passed over the intake, aircrossings were built. One of these was an iron tube and the other was built out of wood.
The shafts were 535 yards deep and the temperature of the strata at that depth was about 78 degrees Fahrenheit and the air was dry and dusty. There were one or two areas where water dripped from the roof or oozed from the floor but the mine was generally dry and dusty.
The explosion occurred a little after 5 a.m. on the 24th May. Most of the men on the night shift which had commenced at 7 p.m. the previous night, had finished their work and had gone up the pit. One of them, John Morgan, the night fireman, had reached the top of the shaft and had stepped out of the cage before the blast reached the surface. Though he was knocked down and inured, he survived. According to those who heard the explosions and saw the effects at the surface, there were three loud reports, the second immediately after the first and the third coming after an interval which was variously estimated at from 15 seconds to two minutes. At the same instant a cloud of dust and smoke issued from the shafts and rose high into the air. The plank floor at each shaft was blown up and a considerable amount of damage was done. of the 83 men and 52 horses in the mine at the time, 81 men and 50 horses were killed. The one man and two horses that survived were near the bottom of the downcast shaft at the time. He was William Harris who the explorers found 160 feet from the bottom of the upcast shaft.
No time was lost making the repairs to the top of the upcast and fan drift. One cage had been damaged and had to be take off the rope and work started with a single gage. Within three hours the first descent was made by the manager, the two day overmen and some others, and by sliding down the guide ropes for a few yards at the bottom where the shaft was blocked, they reached the bottom. It was here that they found William Harris. Mr. J. Dyer Lewis, an Assistant Inspector, arrived at the colliery on the morning of the explosion and Mr Robson arrived early in the afternoon and were joined by Mr. Gray and Mr. White. At least one of the Inspectors or Assistants were underground during the whole of the rescue operations.
They found the mine filled with gas and it was over a week before the west side workings could be reached and only then when the full ventilation was directed into it. The greatest difficulty came in exploring the Pretoria district which was eventually done by reversing the current, partially clearing an enormous fall and sinking through it to the roadway below. Except for a few hours on the 31st. may when it was first entered and the following day when all the bodies were found and removed, the Pretoria district remained full of gas as the return ,which was originally the intake, had become completely blocked by a fall where it rose 1 in 1 through a fault. Mr. Robson commented.
“Some of my assistants and myself were with the parties who first reached and explored the district and it may at once be stated that what we saw proved conclusively that whatever was the initial cause of the explosion, it was not the firing of the shot in the hard heading there.
As is always the case with disastrous explosions in coal mines, it was found that the main haulage roads were damaged and blocked by falls of roof, only here the falls were both high and more continuous than I have ever seen after an explosion in South Wales or elsewhere.
Notwithstanding the enormous difficulties, small passages were made over the falls and the ventilation sufficiently restored to enable several districts to be traversed and the bodies recovered within a few days. At the end of a fortnight, the bodies of all those lost with the exception of three had been found. Two more were reached on the 30th. July below a very large fall on No.2 south engine-plane. These were the bodies of Gwilym Jones, shotfirer and his assistant. They were apparently struck down on their way out at the close of their shift. The firing cable, which was rolled up, and the warming pan with some explosive in it were all found near the bodies. Up to the present time, one body has not been found and it is believed to be under a fall in the Pretoria district where he worked that night and may eventually be recovered”