Slate Quarrying in the Festiniog District

SLATE QUARRYING IN THE FEBTINIOG DISTRICT. 211

SECT.11.-OTRER SELECTED PAPERS.

NO. 1,334.-“ SlateQuarrying in the Festiniog District, North Wales.” By ALFREDANDREW LAXQLEY, &I. Inst. C.E., and CHARLES JAMESBELLAXY. THEREare about twenty quarries at the present time worked, or about to be opened in the district referred to in this Paper, all of which lie within a radius of 2 miles from the terminus of the Festiniog and Portmadoc narrow-guage railway. The workable part of the slate formation seldom exceeds200 feet in thickness; the dip of the strata being to themagnetic north, at an angle of about 30”. The slate itl intersected by veins of green- stone, locally called ‘ hards,’ lying conformably with it, and dividing it generally into four distinct veins, known as the ‘ Flag,’ ‘Upper, ’ ‘ Old,’ and ‘ South ’ veins respectively. The volcanic veins vary from 1 foot to 40 feet thick, sometimes thinning out altogether. They are very hard, being composed of spar, flint, and other silicious compounds, sometimes even of pure flint.The three lower slate beds,viz., the ‘ Upper,’‘Old,’ and ‘ South ’ beds, are from 1 foot to 150 feet thick ; but the L Flag ’ or top rock is often of a greater thickness. The slate from this bed is not of a close durable texture, unless at a great depth; consequently the slates made from it are of an inferior quality, being for the most part ‘ second slates,’ with an uneven surface. Large slabs aremade from the slate in thisbed, but theyrequire planing. The ‘ Upper ’ bed, called also the ‘ Back Vein,’ is of a fine quality, but usually contains a number of thin light-coloured beds, called sand veins, harder than the slate itself, and of a gritty nature. They run parallel to the slate beds, crossing the plane of cleavage obliquely, the cleavage being not quite so true on this account, which detracts from the appearance of the slates, and renders them less saleable than they otherwise would be. The ‘Old Vein,’

known by many as the L Old Festiniog Vein,’ furnishes the finest quality of slates, from which some of the best quarries produce most of their ‘ yield ’ or ‘ make.’ This bedalmost invariably contains the double clay slant, or 9-inchstone. This consists of two beds of soft white clay, each about 4 inch thick, and between P2

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 212 PAPERS.SELECTED OTHER thema bed of slate 9 inchesthick, theregularity of which is remarkable. These clay slants form a reliable guide to the quarrymen, extending, in almosta true plane, over considerableareas, and immediately under them is the superior slate above mentioned. Over the 9-inch stone there is generally a bed of hard unwork- able rock, from 2 to 8 feetthick, which is sometimes made to form the roof in underground workings. In the lowest, called the ' South Vein,' the slate is solid, and as durable as that in the ' Old Vein '; but the surface is rougher, and' the slate does not split so well. It can generally be determined, from the appearance of the slates when manufactured, from which of the four beds above de- scribedthey have been obtained;the beds maintainingtheir characteristicfeatures very uniformly. The slates from each of the four beds in the Festiniog strata are of a bluish colour, and can thus be easily distinguished from the Bangor slates, which are for the most part red, and for this reason often preferred to the Festiniog slates. The phenomenon of cleavage, though occurring in other geological deposits, exists in a more markeddegree in slate than in any other rock ; henco the term usually applied to it, viz., 'slaty cleavage.' It is technically known as the 'split' of the slate, being the direction in which the slate iscapable of being split up intoindefinitely thin lamina. The cleavage planes are entirely distinct from the stratification, and often make a considerable angle with it. The plane of the cleavage in this districtinclines in thesame direction as the dip of the strata; consequently thestrike of the cleavageand of the stratification are parallel to each other. As the dip of the strata is to the magnetic north, at an angle of about 30°, and the planes of cleavage incline downwards in the same direction at an angle of about 45", the cleavage planes make an angle of 15" with the bedding of the strata. There is also a secondary cleavage, in the direction of which the slate is easily, but not so readily, broken, called the ' pillaring ' of the slate. Here, the line of the ' pillaring ' makes an angle of about 15O with the magnetic north (Plate 21, Fig. 2). The plane of the pillaring is in some cases vertical, and in others deviates from it by as great an angle as go", and the walls of the chambers aremade to coincide with it. The above description of the lay of the beds is applicable to most of the large quarries, and is a fair general account of the district, but there are isolated cases where, owing to local dix- turbances of the strata, it might require modification.

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. SLATE QUARRYING IN THE FESTINIOG DISTRICT. 213 The slates are most easily split immediately after the rock is quarried ; the ' Flag Vein ' in particular soon loses its cleavage if

allowed to dry, andbecomes unfit for slste manufacture, for which 1 reason the workmen often cover a block with wet peat to retain the cleavage until they can work it into slates. The slate from the lower beds,which is of a closer texture, retains its cleavage much better, 'and is occasionally sent to London in block. Frost also acts injuriously on the cleavage, and the rock, even before it is quarried, is sometimes injured for :several feet in depth if in an exposed situation. For this reason it is desirable, in severe weather, to cover the workable slate with rubble. Near the surface cracks often occur in the slate, called ' water splits ' ; they are generally of a reddish colour, due to the presence of iron, and slates made from such rock change colour after a time to a dirty green or brown. Although the four slate beds above described are usually of considerable thickness in the Festiniog strata, yet it does not always pay to work them. For instance, where spar occurs the cleavage is often imperfect, being in some cases distorted intoa curve of not more than 6 inches radius. Shining joints, in Welsh coeth,' fre- quently occur in the vicinityof spar. These run obliquely through the cleavage, and cause the slate tobreak. ' Posty ' is a term applied to rock full of joints. These ' posts ' often run parallel for a long distance to the strikeof the beds, that is to say, at right angles to the plane of the dip. They vary in width from a few inches to upwards of 30 feet, and are composed of rock cut up by joints in every direction. Spar from 1 inch to 12 inches thick frequentlytraverses thehard rock in line with these posts. Immediately on eachside of the posts the rock is sound, and solidblocks, 30 feet long, are sometimesob- tained. Faultsand great bevels are also frequentlymet with. In the vicinity of these the rock is generally broken, and unfit for being worked into slates. Great@pars often pass through the slate beds, their general direction coinciding with that of the cleavage. They are sometimesmade use of to form the roof for

the openings. Cubes of sulphate of iron occur in the L hard ' and also in the workable slate ; in the latterfrequently in such minute particles as not to be discovered until after the slates are manufactured ; slates containingit, however, become of a rusty colour after exposure to the weather. Before opening a quarry, it is essential to ascertain the thickness and quality of the slate by driving triallevels : many ruinous blunders have been made- owing to the neglect of this precaution.

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 214 SELECTEDOTHER PAPERS. It is, of course, always a matter of consideration whether it will be cheaper to proceed by the method of open quarrying or by mining. The former system is only advisable where the amount of over- lying rock is comparatively small. In the Festiniog quarries the circumstances are such as to render mining in most cases preferable to open quarrying. The formation of the ground generally enables the water to be drained off by gravitation, and the rubbish has seldom to be raised by machinery. One or more inclines (Plate 21, Fig. 1) have in most cases to be constructed to enable the manufactured slates to be removed from the quarry ; and it can generally be arranged so that the loaded wagonsdraw upthe empty ones. Although bad air, such as occurs in coal mines, is not found in slatequarries, yet it is necessary to provide ventilation to carry away the powder smoke. Mechanical means are seldom requiredfor this purpose, good ventilation in most cases beingobtained by sinking a shaft or driving a level. It is convenient to have several mills for working the slate, one or more on each floor, thus obviating the necessity of raising the blocks from one floor to another. Although steam power is employed at a few quarries, yet waterpower, where it can be obtained, as is usuallythe case, is moreeconomical. Byhaving a water- wheel to each mill, the water is conveyed from one floor-to another, and all the mills on the different floors are worked by one stream. Where it is necessary to lift the blocks from one floor to another, a water-balance is often employed, either working on an incline (Fig. l), or in a vertical shaft. The method of miningand openingout the chambers is as follows :-Assuming that it is proposed to work the ' Old Vein,' and that the 'flint bar ' is to form the roof (Fig. l), a level, A B, (Figs. 2 and 4) is first driven under the ' flint bar' about 7 feet wide, and 7 feet high, in the direction of the strike of the beds as far as the vein is worked out. After this level has been driven a roofing level, about 6 feet wide and 4 feet high, is commenced at the westernmost side of the opening, or ' bargain,' as it is termed, the roofing being more easily worked from this side, immediately under the flint bar (C D, Figs. 2, 3, and 4). Its direction on plan is in a line with the ' pillaring' of the slate, and consequently it makes an angle of about 75" in a westerly direction with the level A B (Fig. 2). Whenthis inclined heading has been ad- vanced some distance the roofing is commenced (C, Fig. a), and is carried forward along the irregular line E F, the heading C D beingkept somewhat in advance. Thisoperation is continued

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. SLATE QUARRYING IN THEFESTIN$OG DISTRICT. 215 until the entire opening, or ‘bargain,’ is ‘roofed,’ the depth being about 4 feet, amply sufficient for the miners to work in. Under the roofing level, C D, a free side, or ‘ ban,’ is cut down in the plane of the pillaring, to obtain a face for the quarrying, the free side being in advance. Sometimes, however, the free side is mm- pleted before the quarrying iscommenced, a favourable bevel joint extending downwards from the roof greatly facilitatingthe cutting, which, in such cases, is not necessarily at the western end of the chamber. When the rockmen commence quarrying out the blocks before the mining is completed, the mining of the roof is kept well in advance of the free side, and the free side in advance of the ,quarrying, theminers usually doing their work at nightso as not to interfere with thequarrymen. The width, C E, of the ‘ bargain’ varies from 30 to 120 feet, and is regulated by the appearance of the ‘ hard ’ forming the roof, and by the position of .the bevels. lpor instance, where the ‘hard’ is solid, and not less than 12 feet in thickness, the width of the chambers may be about 90 feet. The thickness of the wall C H, on plan, is usually about half the width, C E, of the chamber, but in a thick slate bed a wider wall should be left. Duringthe time thatthe works above described arebeing carried forward on floor No. 1, another horizontal level, A’ B‘, is driven,and the same system of mining is carriedout on floor No. 2, and perhaps on floor No. 3. The works on floor No. 1- .should be in advance of the works on floor No. 2, and those on No. 2 in advance of those on No. 3. Care must be taken that the walls and openings are set out in line,so that thevarious chambers may ultimately form a series of openings, divided by the walls which have to be left permanently. The vertical distance between the several floors isabout 50 feet.When the depth is much greater than this, care is required to prevent the slate blocks from $the upper part of the chamber being broken in falling or sliding down.With shallow chambers, on theother hand, the mining work is more expensive, and much slate is destroyed in ‘ cutting the foot’near the level of the floor. In order tomaintain the road A B on floor No. 1, as the slate is being worked out from beneath it on floor No. 2, it is necessary to suspend bridges ofwood plankingby chains or rods to the roof, I K (Figs. 3 and 4). Cross bridges, I L (Figs. 2 and 3), are also hung on ‘the side of the wall. By thesebridges, or platforms, the necessary roads are maintained until the slate is worked out of all the ehambers. In blasting the rock the miners chiefly use compressed gun-

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 216 OTHFJ% SELECTED PAPERS. cotton. A common practice is to charge a hole about 2 feet deep with two cartridges of %-inch compressed gun-cotton, each 1 inch long, with a layerof 2 or 3 inches of ordinary blasting powder over them. This statement, however, applies to the miners’ operations only. The rockmen never use gun-cotton, as it shatters the blocks. Cotton fuse is invariably employed, having quite superseded the straw fuse. For driving a level, or for removing the hard rock, oil of glycerine is effective. The process of quarryingthe blocks is chiefly regulated by the position of the natural joints, or bevels, which occur every 3 to 8 feet in depth, and to which the rock may be worked off.

FIG. 5.

Section through H I on Plan. Before this can be done, however, the rock must be liberated at the foot at the floor of the chamber. If there is no joint runningwith the strike of the beds, the rockmen must ‘ cutthe foot,’ as it is termed; that is, remove by blasting a portion of rock, an operationoften injuring good slate. Cutting machines have been used for the purpose. Having liberatedthe rock at the foot, the quarrymen proceed to cut:out a block by drilling a hole, about 1% inch in diameter, by a jumper. The hole, D E, is made from 4 to 6 feet from the face of the free side, at right angles to the bed, down to the next natural bed joint (Figs. 5, 6, and 7). It is charged to the top with ordinary,powder, no tamping

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. SLATE QUARRYING IN THE FESTINIOG DISTRICT. 217 being used. When fired the rock is generally broken in aline with the pillaring of the slate, the crack probably extending until it meets with a natural cross joint, thus liberating a block. If the first charge is not sufficient to effect this, a second is put in, and sometimes a third. Great care is taken not to employ a stronger charge than necessary, as the block would be much injured thereby, or be what is called ‘powder split.’ An ordinary charge

FIQ.G.

___

Plar..

FIG.7.

41 ? U)

.. -

Section through P Q on Plan. withtamping would render the block quite unfit for slate- making,and perhaps injurethe surrounding slate. The charge is intended justto move the block and no more; so careful, indeed, arethe men in this respect, andsuch confidence have they in the result, thatthey sometimes stand upon the block whilst the shot is being fired. When a bed joint is not met with at a suitable depth a shot, M L, is inserted about 2 or 3 feet into the

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 218 OTHER SELECTED PAPERS. rock from the free side in a horizontal direction, parallel to the natural bed joint (Fig. 7); it is then charged witha depth of 2 or 3 inches of powder and of 2 or 3 inches of tamping, formed of slate dust loosely put in. The shot splits the rock along the cleavage, and the pillar shot is then fired. The slate block thus obtained, about 12 feet long by 4 feet wide, is first split into two parts by a hammer and chisel along the cleavage (Fig. S), then again in the same manner along the pillar- FIG.8.

ing of the slate. If the direction of the pillar split is found not to be quite in theproper line, ahole is drilled through the block in the true line, and a plug and feather inserted to split it. The same process of splitting the block in each direction is repeated several times until it is reduced to slabs about 14inches wide and 4 inches thick, which are now ready for the saw table. If any of these slabs are of too great a length for the table (more than 5 or 6 feet), they are placed across supports and broken in twowith a large wooden mall, beingfirst nicked with a chisel. The operation of splittingthe blocks, intoslabs fit for the 8aw table, is not all performed in one place, being partly done in the chamber or ' bargain,' where the blocks are quarried, and partly at the mill. For instance, the blocks above described would first be reduced into pieces weighing not more than 3 or 4 tons, and then be removed to the vicinity of the saw table, where the process of splitting would be completed. Forthis purpose they are lifted by a crane into trucks, and are then taken to the mill. The slabs are cut to the required length by a circular saw kept wet as it revolves, so that the sawn surfaces may not be heated, otherwise their splitting properties would be impaired; and the table top is drawn forward by a feed-motion towards the saw. Slates measuring 20 inches by 10 inches are worth more per ton than those of either a larger or it smaller size. The slabs from the

saw table are split from the sawn surface along thc cleavage by a fine and broad chisel, with one or two blows of a light wooden mallet. The slab, which is from 3 to 4 inches thick, is first split into two equal thicknesses, and these are repeatedly bisected until they are reduced to laminE. They are then ready for the dressing machine, of which there arc several descriptions. All have a steel bladeabout 3 feet long,which is made torise and Ml, or to revolve over another fixed blade, thus acting like a pair of shears. A gauge is attached to the frame of the machine to insure the squareness of theslates and to regulate their size. Duringthe operation, the slate is held in such a position that the descending blade cuts out the largest slate that the piece will admit of. The dressing machine is generally worked by mill power, but sometimes by the man cuttingthe slates. Only a small portion of the slate is made into slabs forsale. The blocks, when split to the necessarythickness, are sawn round the edges to the size required (when the slate is of good quality with a straight and even split); this completes the operation, the slabs being termed ‘ self-faced.’ When, however, the surface is nottrue, they are planed by a chisel from 4 to 15 inches broad, according to the hardness of the slate. The slate is made to pass repeatedly under the chisel until the surface is uniforn], and the slab reduced to the required thickness. In some of the best bargains ’ in the Festiniog district, the proportion of manufactured slates to rock quarried has been 1 in 4, equivalent to about 1 ton of slates for 2 cubic yards of rock, but the average, proportion is probably only 1 in 5. Under favourable circumstances, 1 ton of slates to 7 cubic yards of rock will pay for working, leaving a small profit. But this does not include the rockremoved by the miners in preparation for the quarrymen. Much skill is required to cut up the blocks to thebest advantage. A slate block of a favourable shape, weighing 1hon, will, with care, produce about 3 ton of slates, but, on the average, such a block would only produce about 4 ton of manufactured slates. From 20 to 90 tons of slates per month may be obtained from each ‘ bargain,’ depending upon the quality of the rock. Sometimes a wide chamber is let in two contracts or ‘ bargains.’ A chamber 60 feet wide might be so let. Formerly, and even now at some quarries, the slates wcre made entirely by hand without sawing tables or machine slate-dresscrs, and much waste was the result. The slabs were broken across by a large mallet, and cut by hand with a heavy knife. The rubbish from the chambers is removed to the tip in wrought-iron wagons, weighing about 10 cwt. and holding

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 220 OTHER SELECTED PAPEBS. about 50 cwt. The wheelsof the wagons areeither single flanged fast on the axle, or double flanged loose on the axle ; the latter are better suited for sharp curves. The tramways for the transport of the blocks and rubbish are of a simple kind, and not unfrequently consist of flat wrought-iron bars let into oak cross sleepers ; a convenient form of rail on sharp curves. The cost of a sawing table and slate-dresser is about S60, and they work about 1 ton of manufactured slate per day on an average, but with good rock much more. A sawing table requires 3 HP. to drive it, but the power varies according to the sharpness of the saw and the hardness of the rock. The saws are sharpened twice a day. They make fifty revolutions perminute, andthe feed-motion given to the tableis about 6 inches per minute ; sand saws are now seldom used.

The level, which is driven at the commencement of the work, (A B, Plate 21, Figs. 2 and 4) measures about 7 feet square, and is generally let to the miners for 52 10s. peryard forward. This price includes the cost of removing the rubbish to the tip, and powder and other stores. Two miners work together at the face, single hand drilling. With two shifts they drive about 15 inches in twenty-four hours. Four holes, 2 feet deep, constitute a day’s work. The average cost per lineal yard of heading is- S. a. d. Labour-fourmen, 9.5 days at 4s...... 1 18 0 (Candles ...... 0 2 0 Fuse...... 0 10 Stores Gun-cotton Stores ...... 0 3 0 Black powder ...... 0 3 0 iSmith ...... 0 0 6 Removing rubbish to tip, 10 tons at 4d...... 0 3 4 Sick fund, 1s. per man per month ...... 0 0 4

62 11 2

The expense, however,varies from S2 to S3 per lineal yard,according to the direction of the heading, the lay and hardness of t.he slate rock, the quality of the roof, and the number of joints. The cheapest description of levelto drive is one runningwith the strike of the ,beds, with a good clay slant for a roof,also in ‘posty ’ rock. The average progress with two shifts of two men per day is from 8 to 12 lineal yards a month. The miners often work three shifts of eight hours per day, and under these circumstances, in favourable ground, the rate of progress has been 22 lineal yardsin five weeks-about 18 lineal yards per month.

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. SLATE QUARRYING IN THE FESTINIOG DISTRICT. 221 In the ‘ flint’ or ‘ hard rock, in which nitro-glycerine and gun- cotton are effective, the cost of a level 7 feet square in sect.ion varies from $6 to 69 per lineal yard. With two shifts of miners the progress is from 3 to 5 linealyards per month. Fora level 6 feet by 4 feet the cost is from S1 to S2 per lineal yard, according to the character of the roof. With twoshifts of one manper day the progressvaries from 6 to 12 lineal yards per month. For widening the roofing the charge is from 5s. to 8s. per super- ficial yard, including thestores and labour, butexclusive of moving the rubbish to the tip. The lower price is paid when under a clay slant roof. Several men may be employed at the same time at this work. Should the rock be of such quality as to be useless for slate-making, the cost of quarrying and removing it as rubbish to the tip will be, approximately, Per- Ton. d. Quarrying ...... 5 Removing to tip . . . . 4 9 or about Is. 6d. per cubic yard, the - contractor finding powder, &c.

If, however, the slate has to be quarried from an unfavourable position, the cost may be 2s. per cubic yard, or more. A ‘bargain’ ready for work may be let to the contractor in several ways :- 1. The contractor may be paid a price per ton on the blocks quarried ’and taken to the mill, together with a price per ton for rubbish quarried and removed to the tip, and also a price per mille (or nominal thousand) for manufactured slates. 2. A price per ton for all rock quarried, whether taken to the mill or removed a8 rubbish to the tip, and a price per mille for manufactured slates. 3. A price paid to the contractor on the manufactured slates, to include the cost of quarrying, &C. Supposing the rock to be of such quality that 1 ton of manufactured slates can be obtained from 7 cubic yards, or aratio by uFeight of 1 in 14 ; then, if the bargain is let to the contractor on the plan indicated by the second of the above-named methods, the prices paidto thecontractor would be about 6d. per ton for all rock quarried, together with a price per mille for slates made, equivalent, in the presentinstance, to 208. per ton of manufactured

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 222 OTHER SELECTED PAPERS. slates. Under these circumstances the expense per ton for quarrying and making slates is, approximately,

E. 8. d. Blocks quarried and rubbishremoved from the at 6d. , quarry to the tip ...... i” Price paid on the manufactured slates ... 1 ,, 20s. 1 0 0 -- Total amount paid to contractor. .. 1 7 0 Add for mill rubbish taken from the mill to ) 4 ,, 4d. 0 1 4 the tip ......

Total cost perton of manufactured slates . 31 S 4

This price is exclusive of the cost of preliminary operations, snch as opening out the ground and driving thelevels. The charge for these varies so much with each quarry that it would be im- possible to reduce it satisfactorily toa price periton of manufactured slates. The cost per ton of slates given above, viz., 51 88.4d., is for a yield of 1in 14. For a yield of 1 in 7 by weight, the cost of manufactured slates might perhaps not be more than 15s. per ton. With a good yield of rock, as in thiscase, the mode of payment described under the third method is the best to adopt, viz., to pay the contractor only upon the slates made, in order to induce him to waste as lit,tle rock as possible. When the yield of the rock is poor, however, the contractor is generally paid according to the system given under methods 1 and 2. In exceptional cases, where the slate-making is let as a distinct and separatecontract from thequarrying, the cost, including splitting up the blocks andsawing and dressing the slates, is 10s. per ton. The price paid to the contractor per mille on the manufactured slates varies from time to time, and depends also upon the size of the slates. In order to simplify the calculations, the following method is generally used. Certain standard prices are assumed for each size of slates;thus, for a large slate 24 inchesby 14 inches, the standard or nominal price is 30s. per mille ; for slates measuring 20 inches by 10 inches, 20s. ; for a slate 14 inches by 10 inches, 10s. per mille ; and for intermediate sizes thereare intermediate prices. Thenthe number of slates of each kind being estimated at these nominal prices, and the amounts added together,the sum of the whole is increased by a certain per- centage, called ‘ poundage,’ agreed upon for that particularbargain. Thus a ‘pound poundage ’ is equivalent to adding 100 per cent., or doubling the nominal amount. This poundage varies from

Downloaded by [ University of Liverpool] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. SLATE QUARRYING IN THE FESTINIOG DISTRICT. 223 5s. to 254 andis therefore equivalent to addingfrom 25 to 125 per cent. to the prices given above. The cost of slab manufacture, exclusive of quarrying, is as follows :- Per Super. Yard. d. Splittingup and sawing the block .....5 Planingboth sides ...... 4 - Total cost ...... -9 For slabs l& inch thick thisis equivalent to 10s. per ton. The average wages made by the men are :- Per- Day. S. d. Slate-maker or planer ...... 6 0 Miner ...... 4 0 Labourer ...... 3 6 A mille is more than a thousand slates ; for instance, the quarry- man as a rule gives to the quarry 1,300 slates to the mille ; the quarry send to the wharf for shipment 1,280 per mille; and the wharf ships 1,260 per mille to the merchant, who in addition is allowed 12 per mille to cover breakage, but this is a matter of arrangement between the buyer and seller. The breakage in transit is not always covered by the above allowance of 12 per mille, especially if the slates are not quite straight. The proprietors of the quarries are almost exclusively English- men; but the quarrymen are entirely Welsh, only about 2 per cent. of them speaking English. Although some of the quarries returnlarge profits totheir proprietors, many of themare at present worked at a loss. The largest and most profitable is that owned by theWelsh Slate Company, which ships about 40,000 tons annually. The entire produce of the Festiniog district is 140,000 tons per annum, representing an annualvalue of between ~€400,000 and 5500,000. The slates are conveyed bythe 2-feet gaugerailway from Festiniog to Portmadoc. The full wagons run down by their own gravity,the gradient being a descending one allthe distance. About 120,000 tons of slateare shipped from Portmadoc, some to London, but for the most part to the Continent, where the blue varieties arepreferred ;the remainder go by rail tovarious parts of England. The communication is accompanied by a series of sketches, from which Plate 21 and Figs. 5, 6, 7, and 8 have been compiled. [APPENDIX.

APPENDIX.

LISTOF AUTHORITIESOR SLATEAND SLATEQUARBYING. Anonymous. A few words on Slate,Slate Quarries, andSlate Quarry Com- panies.” By a Man of Experience. Bower, John. ‘‘ Slate Quarries aa an Investment.’’ 8vo. London, 1865. Hughea, Samuel. “ The Bangor Slate Quarries,” WeeIe’s ‘‘ Quarterly Papers on Engineering.” 4to., vol. iii.,1845.

Rellow, Joseph. “ The Slate Trade in North Wales.” 8vo. London, 1868, Ramsay,Andrew C. “Memoirs of the Geological Survey of Great Britain,” vol. iii. “ The Geology of North Wales,”p. 75. 8vo. London, 1866.

Smith, T. Cooper. ‘l Slate Quarries in Walesconsidered a8 an Investment.”