Historical aspects of the Welsh slate industry

D Dylan Pritchard MA FSS


During the eighteenth century the quarries were nothing more than shallow excavations and the adventurers were for the most part quarrymen‑farmers or small merchants with little or no capital at their disposal. Their methods of production were primitive in the extreme ; the heavy iron crow‑bar with which they loosened the slate blocks from the rockface, their unskilled method of pillaring the rock and their rudimentary efforts with clumsy tools to convert the slate blocks into slates, were hardly calculated either to utilise the rock economically or produce a highly finished product.

As the excavations grew in depth man‑operated turn-trees were introduced to raise the blocks and rubbish to the brink of the quarry; here the buckets of waste rock were emptied into wheelbarrows to be tipped but the slate blocks were almost invariably carried upon the quarrymen's broad shoulders (which were protected by a leather jerkin), to a clear space where they could be conveniently converted into slates. The slate rubbish was deposited as near the margin of the pits as possible in order to reduce labour costs, so that as the quarries were extended, falls of rock from the sides were common and proved a danger to the lives of the workers and a hindrance to the successful working of the pits at later stages. This defective and short‑sighted mode of working greatly impeded subsequent development and added materially to the capital expenditure involved in opening out the Penrhyn, Dinorwic, Cilgwyn and other large quarries.

Many improvements in production methods occurred during the first quarter of the nineteenth century. Very little change, however, took place in the quarrymen's tools; the dressing knife was improved so that it could be used to trim the thinner and larger sizes of slate, but the heavy iron crowbars employed to extract the slate blocks from the rock face, and the rock chisels and sledge hammers used to subdivide the blocks into suitable sizes for conversion into slates showed little modification. The quarryman's knowledge of the nature of the slate rock and the most economical methods of working it undoubtedly progressed greatly, but the heavy fines levied for producing defective slates and the frequent complaints of merchants that the slates were irregularly trimmed and undersized, testify to the fact that the craft skill was not yet perfected.

Excavations were getting deeper and horse whinneys were introduced generally to hoist the slate instead of the man‑operated turn-trees formerly used. In 1829 a water‑balance was erected in the Tal y Sarn Quarry, Nantlle, which raised the slates up a vertical shaft and this contrivance was later adopted in some other quarries. Considerable difficulty was experienced in ridding the workings of water, and water‑wheels and windmills were erected in the Nantlle quarries to pump the water. In 1807 the first steam pump in the history of the industry in North Wales, was installed at the Hafodlas Quarry, Nantlle. In 1816 £550 8s. 11d. was paid for a machine to saw slates in the Dinorwic Quarry; similar sawing machines driven by water power were used in the Penrhyn and Diphwys Quarries. Inclined planes and tramways were constructed to facilitate locomotion within the quarries ; these soon superseded the wheelbarrows, but the latter were still in use to clear rubbish in some parts of the Dinorwic Quarry in 1831. In some quarries small rudely‑constructed huts were erected upon the rubbish tips, where splitting and dressing operations could be conveniently carried on, but in most quarries these operations were still carried on in the open. Cornish miners working in the Welsh copper mines had initiated the quarrymen into the mysteries of blasting rock with black powder.

The smaller quarries introduced improved machinery before the larger quarries, but the latter developed their workings along more scientific lines ; this apparently paradoxical state of affairs can be explained. The removal of the rubbish which had accumulated upon the valuable strata during the eighteenth century, and the clearing of top‑soil and unproductive rock so that the numerous small pits, which had formerly worked pockets of the slate vein, could be merged into one great quarry, involved considerable capital expenditure. In the Nantlle district the capital resources of the quarry entrepreneurs were limited, the lie of the land, as well as its sub‑division into small properties, made it difficult to work the pits in regular terraces, and the leases were such as to discourage the sinking of capital in work which was not profitable within a comparatively short period. The duration of the leases never exceeded thirty‑one years, and sometimes they were as short as five years; the Cilgwyn Company, for instance, sub‑let the workings upon Cefndu common for short periods to numerous small capitalists and this made it impossible to develop them properly. Royalty payments were high, rarely less than one‑tenth the value of slates on the quarry bank. In many leases it was provided that upon their termination the lessees could either remove any machinery they had erected or sell them to the lessors at a fair valuation by impartial persons, but there was no compensation for capital spent in removing top rock and forming galleries and so this description of work was cut down to the bare minimum. The cumulative result of these factors was that the smaller productive units frequently introduced improved machinery with the intention of extracting as much good slate as possible during the term of their lease, but they did not under take the expenditure upon dead work which was necessary if the quarries were to prove profitable over a long period. During depressed years the unproductive rock was left in situ so that the sides of the quarries were undermined ; this made falls of rock and rubbish into the quarries inevitable. In 1817 a steam pump and two whimsies fell sixty yards into the Hafodlas Quarry and within a few days the workings were flooded. In 1823 over 20,000 tons of waste fell into the Cilgwyn Quarry. These disastrous falls were due solely to economy of capital expenditure.

The Penrhyn and Dinorwic Quarries had been taken over by the landed proprietors since 1782 and 1809 respectively. They had no royalty or dead rents to pay nor any lease which might terminate their activities, so that they could take a long period view of things. Their capital resources were considerable and their quarries were extremely productive and conveniently situated on mountain slopes which facilitated economical development on a large scale. It was James Greenfield, who became manager of the Penrhyn Quarry in 1799, who first conceived the idea of working the quarry in regular galleries or terraces along the mountain side. The introduction of this method saved consider able quantities of excellent slate rock which had formerly been shattered by falling from great heights to the bottom of the excavation. From the middle of each terrace there was a slight decline in each direction so that loaded wagons ran easily along tramways to both extremities, and this materially reduced the cost of tipping rubbish and of conveying slate blocks to the dressing sheds. He also carefully ascertained the extent of the slate strata so that rubbish should not be deposited upon it. The terrace system was expensive to introduce, and there remained always the temptation to work only the lower galleries where the slate rock was most productive. In 1822 we learn that the commencing of new galleries at the head of the works had been too tardy since the depression of 1814. One Government report states that Mr. Greenfield's plans to remove top‑rock and prepare for further galleries apparently did not "receive the necessary sanction for enabling him to follow up his intentions," with the result that he had to put men to work "in high and dangerous situations on the edge of the deep quarries," and rubbish fell into the quarry and destroyed the principal inclined plane. The gallery system was also adopted in the Dinorwic Quarry, and by 1830 five terraces were gradually being carried out of the sides of the mountain. The quarrymen's craft skill, the machinery and capital equipment employed and the methods of developing the quarries, all registered radical improvements during the first quarter of the century.

The following half century witnessed revolutionary changes in production methods. The tools employed by the rockmen in extracting slates from the rock face and by the miner in driving levels and sinking shafts were greatly improved. The safety‑fuse made the use of explosives safer ; dynamite, nitro‑glycerine and other powerful explosives were introduced for the driving of levels and the removal of unproductive rock. In some of the Nantlle quarries in the 'seventies Dixon's boring machine, operated by manual labour, was used to prepare holes for large charges of powder ; the Burleigh rock drill was introduced successfully into the Cambrian Quarries, Llanberis, effecting a saving of about 25 per cent. in costs. Boring machines and rock drills were still very uncommon in the 'seventies and had not been introduced into the Festiniog mines or the larger Caernarvonshire quarries.

By the 'seventies the tools used for the splitting and trimming of slates by hand had assumed their present day shape and form. Several kinds of slate dressing machines worked by manual or water power had been invented and introduced generally into the Merionethshire mines. In the Nantlle quarries all the slates were trimmed by hand and the same was true of all the other Caernarvonshire districts except that a few slate dressing machines were in use in the Penrhyn and Dinorwic Quarries. In the Aberllefenny Quarry a treadle machine invented by the quarry manager was being used for splitting slates.

One of the most important innovations was the sawing machine; this was used for sub‑dividing blocks into suitable sizes for splitting and dressing into slates. This resulted in considerable saving of good rock and facilitated the task of the splitter by providing him with smooth ends, instead of jagged ends, to work upon. By the ‘seventies sawing machines had been introduced generally into the Merionethshire mines, and to a few of the major Caernarvonshire quarries. The reason why they were adopted so quickly in the Merionethshire mines and so tardily in the Caernarvonshire quarries is chiefly geological and not economic; in the latter the slate had so many natural foot‑joints that the slate could be removed from the rock face in conveniently sized masses for pillaring into suitable blocks for the splitters, whereas in the Merionethshire mines such convenient natural joints were not so common, so that the masses of slate released from the rock often weighed several tons and the difficulties of pillaring it into blocks was greater; this difficulty was overcome through the introduction of sawing machines. In the Caernarvonshire quarries the splitting and dressing was done in rows of little huts, but in the mines of Merioneth it was frequently the case that the sawing, splitting and dressing operations took place in one large shed so that the sawn blocks could be handed directly to the splitter.

Water balances, inclined planes, and steam engines were used to hoist slate in the mines and quarries. Tramways were laid down throughout the workings and in the larger concerns locomotives were used to haul rubbish, but the greatest part of the haulage work was still done by horses. The internal organisation of the quarries in all districts showed remarkable improvement. Mechanical devices of all kinds were being introduced, particularly into the slate mines of Merioneth.

There were three methods of working‑the vertical excavation method, as in the Nantlle district, the gallery method as in the Dinorwic and Penrhyn Quarries, and the mining method, as in the Festiniog district. The Penrhyn Quarry was still being developed on the lines set down by Mr. Greenfield, and in the 'seventies there were sixteen galleries. Six water-balances hoisted rubbish and slate from the lower galleries which were below ground level. Large hydraulic pumps kept the workings clear of water, and locomotives were gradually displacing horses on the more important floors. The quarry was not worked regularly throughout and some of the higher galleries were exceedingly narrow, and in 1872 there was a tremendous fall of rock which restricted production for some time. The sister quarry on the other side of the Elidir - Dinorwic Quarry ‑ had throughout the century been worked more irregularly. Even in the 'seventies the galleries were of different widths, depths and levels; rubbish which had been allowed to accumulate in former years upon the slate vein still remained to be cleared in some parts, although care was now taken that new rubbish was either tipped into the nearby lakes or upon the hard Cambrian grit to the south of the quarry; worthless parts of hard rock were left standing and these hindered the working of the slate vein on regular lines. There was an excellently equipped iron foundry attached to the quarry and all the machinery required, such as iron furnaces or wagons, were produced on the spot ; the driving power for this foundry was derived from an enormous water‑wheel.

In the Festiniog area the slate vein had to be followed underground and this was the most potent factor which retarded the development of the district during the first quarter of the nineteenth century. Diphwys was the only concern where a considerable quantity of slate could be quarried without underground workings or removing a tremendous head of super-incumbent rock and so it was the first concern in the area to be worked on a large scale. A fortune had to he spent on most of the other Festiniog mines before they became profitable undertakings. The slate mines were worked in underground chambers with pillars or continuous walls of rock to support the roofs. Under this system of working the proportion of rubbish to roofing slate was much lower than in open quarries, but, on the other hand, the supporting walls and pillars were of good slate rock so that about one‑third the production slate could not be extracted at all, although the miners frequently succumbed to the temptation of undermining the pillars and walls and making the chambers too wide.

The first three‑quarters of the nineteenth century was a period of experimentation and innovation in the history of the slate industry. The same remark holds true, of course, of most other industries during those years and progress in the realm of science was being successfully harnessed to the peculiar needs of individual industries, bringing about revolutionary changes in methods of production, transport and marketing. It was the revolutionary changes in production methods which made it physically possible for the slate industry to increase the volume of its output so rapidly, and which helped to keep costs of production low sq that slate could be marketed at a price substantially lower than that of competitive materials.



Aspects of the Slate Industry 15: The Expansionist Period 5

Quarry Managers' Journal July 1944