Chapter II: Part 2

The slab, or grindstone, is generally of marble or porphyry, and must have a perfectly smooth surface; and the muller is a large oval or egg-shaped pebble, with one end broken off, and the surface made as smooth as that of the slab. A small quantity of the colour which requires grinding is placed on the stone, and moistened with a little oil; and the muller is then worked over it, by a circular movement, until it is gradually driven to the edge of the stone. The colour is then removed by the spatula, or palette knife, and placed in the paint pot.

In this state, however, the colour is too thick to use, and of course requires to be thinned by adding the oil until it is sufficiently fluid.

In painting woodwork, the first business is called “knotting,” that is, removing the turpentine from the knots, which would otherwise ooze and spoil the paint. They are first covered with fresh slaked lime, which dries up and burns out the turpentine; this is afterwards scraped off, and the knots painted with a mixture of red and white lead mixed with glue size, and afterwards with white lead and linseed oil. When dry, they must be rubbed smooth with a piece of pumice stone. The next operation is to put on the “priming,” which is the first coat of paint, composed of red and white lead and linseed oil. The nail-holes, and other imperfections, are then stopped up with putty (a mixture of linseed oil and whiting, made into a paste), applied with the _stopping knife_; and then the other coats of paint are laid on; three coats being generally considered sufficient; and the last being of the required colour.

The brushes used by the Painter, are either round or flat, the latter being used in varnishing or graining; they are made of hog’s bristles. The smaller kinds of brushes are called _tools_ or _fitches_, and are used for small surfaces, such as ornaments and mouldings round panels, when the colour is generally taken from a _palette_—a round slab of wood, with a hole through which the thumb of the left hand passes in order to hold it. The brushes must never be allowed to get dry, but when not in use must be kept in water: it is always best to keep a brush for each colour. Another part of the Painter’s business which requires more skill, is graining and marbling; or the imitation in colours of the marks and grains of various kinds of wood, and the veins and spots in marbles. This is of course a part of the trade which requires a knowledge of the thing to be imitated, and great care and taste in doing it well.

Graining is generally done with “distemper colour,” that is a kind of paint in which whiting and size are used instead of white lead and oil, for the basis of the colour; but the colours depend on the sort of grain to be imitated, and they are applied in various ways and with different sorts of brushes, some of the colour being occasionally removed with a piece of wash leather, in order to give the appearance of the light marks seen in the “heart” of the wood. The appearance of the “grain” of the wood is effected by the _graining comb_, a comb with short thick straight teeth, which is drawn along the paint in a wavy line.

Marbles are imitated in oil if it is outside work and exposed to the weather, but for inside work distemper colour is frequently used.

Occasionally walls are coloured in distemper, and it then frequently happens that a pattern or some ornamental design is painted in the centres of the panels, or round the mouldings. This is a part of the Painter’s trade which requires much skill, and a knowledge of artistic drawing and design.

Varnishing is an operation requiring great care to perform it properly, since it is necessary not only to choose the right kind of varnish, but also to apply it to the surface of the paint with a light but firm hand. Varnishes are made of gums or resins melted, spirits of wine, oil of turpentine, or strong white drying oil. The hard varnishes dry rapidly, and are made of the harder kinds of gums, such as copal, mastic, &c., and the soft of Canada balsam, elemi, turpentine, &c. The most useful for the House Painter are those of copal, linseed oil, and turpentine.

The brushes used in varnishing are generally flat, so as to enable the workman to lay an even surface on the work. Varnishes are usually kept in wide-mouthed bottles; from which they are poured into little tin pans with a false bottom above the real bottom, the space between the two being filled with sand. The use of this is that when the pan is placed over the fire, the sand becomes heated, and the varnish is kept a long time from becoming chilled.

The trade of the Glazier, though now very important, was unknown in this country till the eleventh century, and even long afterwards the use of glass for windows was extremely rare; pieces of horn, and oiled paper, supplying its place in almost every building except palaces and churches. As we have here to do with the Glazier, and not with the manufacturer of glass, we need say little about the method of making the materials used; so that it will suffice to know that the “crown glass,” mostly sold for windows of houses, is composed principally of white sand, pearlash, and saltpetre. This glass the Glazier purchases in sheets of a circular form, each of which is called a _table_, since the mode in which it is made renders such a shape necessary; and the first thing he has to learn, is how to cut out square pieces of the proper size without wasting much of the round edge. The glass when cut is fixed either into lead work or sashes; the former of these is the oldest description of glazing; and in the common kind the leaden frames are soldered together, so as to form squares or diamonds; the sides of the grooves in which the glass is placed being soft enough to bend back to receive the panes, and then bend back again to hold them firmly. In wooden sashes, such as are now commonly used, the space or frame for each pane of glass is “rebated,” that is, it has outside a small groove all round to receive the pane, and a ledge against which it rests. In this “rebate” each square of glass is placed, and then firmly bedded and fastened smoothly with a rim of putty filling up the groove.

The Glazier uses a _hacking knife_ for cutting out old putty from broken squares; and the _stopping knife_, or _glazing knife_, for laying and smoothing the putty.

For setting glass into lead work, the _setting knife_, or _chisel knife_, and the broad-bladed knife is used.

As much of the Glazier’s work is done outside the house, he is sometimes compelled to use a board which is fastened with screws, and projects from the window so that he may sit astride on the outside. No one should ever attempt this where the sash can be easily taken out and the work done inside.

The rest of the Glazier’s tools are a _square_, and a _straight edge rule_ for cutting against, a _two-foot rule_, and compasses for measuring; _pincers_ for breaking off the edges of glass that have been partially cut through; and the _diamond_, which is used for cutting, and is his principal tool. This is made of a small unpolished diamond fixed in lead, and fastened to a handle of hard wood.

THE PLUMBER.

In trades connected with building, the work of the Plumber is of so much importance that it must come next to that of the Bricklayer, and the Carpenter. At one time the Plumber (who takes his name from the Latin word for _lead_[2]) was principally employed in making leaden roofs of churches or large public buildings and in forming casements for windows; window frames being then made of strips of lead soldered or riveted together and holding the little diamond-shaped panes of glass between their edges. In those days all the water used in the house was carried from the well or from the conduit in the main street, or was brought in casks set upon wheels from the nearest running stream: while rain-water for washing was collected in tubs or vats as it ran off the roofs. Not much more than a century ago the poets wrote of the misery of the streets of London on a wet night, when there were no waste pipes to carry off the rain from the overcharged gutters on the tiles, and nobody could venture out of doors without being half drowned by the sudden discharge of a shower bath from some overhanging gable. Then, as there was no proper system of pipes for carrying off the wet, there was very little drainage except by means of open gutters, and the bye-ways, as well as some of the principal thoroughfares and large houses, were extremely unhealthy.

[2] Plumbum.

We are not quite perfect even yet in these respects, and there are still neighbourhoods in London where a few Plumbers might be able to make vast improvements; but we are a great deal better off than our great grandfathers were. The Plumbers do not make quite so many leaden casements as they made in the olden time, but they are well employed in constructing roofs; carrying water into houses by means of leaden pipes; making cisterns to contain a good supply of it, and providing other pipes and gutters for conveying all the dirty water and drainage into the sewers that are under the roadway, where it runs quite away from the streets, and (in London at least) goes into the sea from near the mouth of the Thames at Erith.

Now as the Plumber has to do a great deal of his work in roofs and other places where he is liable to fall, he should be clear-headed, and able to go up a ladder or look over a ledge at a height from the ground without being afraid, and this is all the more necessary because he has to handle tools, and sometimes to pour melted solder out of a hot _iron ladle_ while he is at his work on these places. For the purpose of melting the solder he has to carry his _fire grate and melting pot_ with him to some place near where he is at work, since unless the solder can be used rapidly it cools, and will not make a sound joint. The rest of the Plumber’s tools are the _pouring stick_ for applying the melted solder in the places where it is required, the _soldering iron_ which is made red-hot, and passed over the soldered joints to smooth them and make them all firm and sound; the _chisel_, _shave hooks_, _drawing knife_, and _chipping knife_, for cutting the lead and scraping it on the surface, or at the edges that are to be fastened together; the _hammers_ and _mallets_ for beating the lead into shape and flattening the ridges, the _bossing mallet_ and dresser for bringing the sheet of lead to a proper shape, and forming it over the ridge of a roof, the _chased wedge_, the screw-driver, the _dunring_ and the _turnpin_ for various uses in making roofs, laying down leaden pipes and fixing taps, and the _sucker hook_ used in repairing or fixing pumps when the part of the pump called the sucker requires to be rectified.

There are other tools beside these, such as planes for making the surface of the lead smooth and even, gouges and centre-bits for circular openings in the lead to receive nails or clamps, measuring rules and compasses, and pads of carpet or cloth to hold under a pipe when it is being soldered, that the solder may be pressed round the joint before it cools, and without its dropping on the ground.

Plumbers now buy their sheet lead as well as their leaden pipe at the warehouses, but those in a large way of business formerly cast the lead themselves. For this purpose they used a casting table, which is a great wooden bench about six yards long and two yards wide, made of smooth planks, and with a raised wooden frame round the edge. On this table the Plumber spreads a layer of finely-sifted sand, which was made level by a strike—a flat piece of wood with two handles—drawn from end to end of the table; after this the surface was made still more smooth by a planer, which was a flat plate of copper fastened to a handle.

A trough called the pan ran along the whole length of the table, and into this the melted lead was poured from the melting pot. There were two ways of making the sheet lead: one of them was to tilt the trough up, and pour out the lead on to the table, two men immediately passing a wooden strike over it so as to spread it evenly over the whole surface. In this case the thickness of the sheet of lead depended on the distance between the edge of the “strike” and the surface of the sand. Another way was to have a narrow opening all along the bottom of the trough, the trough itself moving from end to end of the table as the lead flowed out. When this method was used the thickness of the sheet depended on the size of the opening, and the rapidity with which the trough was moved along the table. Neither of these methods are now used, the lead being rolled into sheets by machinery.

Water-pipes are made by lead being cast in moulds with a steel rod passing through their middles, according to the size required. The lead is poured into the space between the rod and the mould. After it is cool the rod is drawn out by machinery, and the mould which is made in halves is opened and the pipe taken out. The pipe is then much thicker and shorter than is required for use, but it is afterwards drawn between powerful iron rollers with grooves cut in their surfaces, an iron rod being again placed inside it. As these grooves gradually decrease in size, and the pipe is drawn through several, it is very considerably lengthened, and at the same time diminished, in thickness, by the time the operation is finished. Another method of making lead pipes is by the use of the _forcing pump_, which pumps the melted metal out of the boiler into a mould containing a “mandril,” or pipe of the required size. Pipes made in this way do not require to be rolled.

The work which the Plumber is called upon to do on the roofs of houses requires experience before it can be properly performed. The foundation of the roof which is to be covered with lead is made either of boards or plaster, so that the surface may be even, and if it be of boards they must be thick and well seasoned to prevent their warping. The foundation slopes a little in order to carry off the rain towards one end. When the roof is so large that it needs two widths of lead, there are three ways of joining the edges of the lead together: one is by fastening to the roof long slips of wood (flat at bottom and round at top) at the places where the lead will be joined. Over these strips the edge of the first sheet of lead is folded and hammered down quite close, then the edge of the second sheet is folded and hammered over that, so that water cannot get between them. This is called “rolling.”

Another method is to bring the two edges up just as though they were to be sewn together, then to fold them tightly one over the other, and hammer them down: this is called “overlapping,” but it is not so good as rolling for keeping out the rain.

The third way is to _solder_ the edges together: the solder, which is in constant use by the Plumber, being a metal made by mixing lead and tin together. These two metals when mixed adhere very strongly to the lead that they are meant to join, and the surface to which they are applied is made hot enough to unite with the solder by means of the soldering iron, while very often a little resin, borax, or tallow is placed on the surface of the lead to cause it to combine more rapidly with the molten metal.

Besides the fixing of roofs the Plumber makes leaden cisterns, fixes rain-water gutters, and waste pipes, and arranges taps and drains; and in some of these operations he will use zinc instead of lead. Not the least important part of his business, however, is the construction and arrangement of pumps, and for this purpose it is necessary that he should study mechanics, and those branches of science which refer to the properties of water, and to the laws which govern the air and other fluids. He is always the best workman who goes to his business with a knowledge of the natural laws and scientific facts connected with it, and a very little study will save a world of blundering; during which the ignorant man will remain a labourer, because it takes him half a lifetime to learn his business.

THE GASFITTER.

As there are now few large houses which are not lighted by gas, the trade of the Gasfitter is one of considerable importance; and though the materials used are generally bought ready made from the Brassfounders, the glass-works, the Ironfounders, or the lead warehouse, considerable skill is required, as well as some taste in properly adapting the chandeliers and burners, and skilfully adjusting the tubes and pipes so that they may easily be repaired, or any escape of gas quickly detected. The various tools used by the Gasfitter are simple enough, but careful practice is necessary for their proper use; and, as any flaw or imperfection in the work may lead to very dangerous consequences, all the operations should be thoroughly tested, and every joint and fitting in the various parts made sound and strong.

Before the gas is taken into a house, or as it is called in the trade “laid on” in the house, it is of course necessary to obtain the permission of the Company to whom the works where the gas is made belong, and to agree to pay for the quantity that is burnt, which is charged by the thousand cubic feet, and varies in price according to the cost of the coal from which it is made, and the difficulty of conveying this coal to the works.

The first operation is to take up the roadway in front of the house, in order to connect the pipe which is to convey the gas to the meter with that which conducts it from the works to the different streets of the neighbourhood. For this purpose the _spade_ and _crowbar_ are necessary, while sometimes the pickaxe also has to be used; and the _rammer_ serves to beat the earth down more closely after the pipe is laid.

The pipe which is joined to the larger pipe, or _main_, is generally of iron, and is made with a screw and socket, that it may not be easily displaced by the pressure of the roadway or footpath, and this, passing into the basement of the house, supplies the gas to the _meter_. The meter is a mechanical contrivance, which is so constructed that the quantity of gas passing through it is registered by a plate something like a clock face, with a hand to point to the figures which represent the number of cubic feet consumed. There are different kinds of meters, and the construction of them varies very considerably, but they all answer this purpose: so that when the inspector visits the house once a quarter he may directly see what quantity is to be charged for. The pipe leading from the meter is fitted with a strong tap, by turning which, all the gas may be shut off from the tubes that convey it to the different burners in the house, and from this pipe the smaller pipes (made of a sort of solder or of lead) are taken to the various rooms. In order to carry the tubes through a wall, it is necessary to use the _brick bit_ and the _brick auger_ for boring a hole to receive it, while to support it against a wall or along the top of a ceiling the Gasfitter uses _wall hooks_, the _hammer_ and the _tongs_ for holding and bending the pipe to its proper direction. In kitchens and basement rooms the pipe is generally carried from the meter up the wall and along the ceiling to the place where the burner is to be fixed: but in upper rooms the pipe is taken up the house wall, and carried under the flooring of the room above to the centre of the middle joist, where a hole is bored quite through the ceiling of the room below. For this purpose the _twisted auger_ is generally used; and for the preliminary work of taking up the floor and cutting a groove in the joist to receive the pipe, that it may not be injured by the pressure of the boards above, the _saw_ and the _hammer_ are required.

Of course one length of pipe is not sufficient to go to any great distance, and a joint has frequently to be made, the solder used for this purpose being so easily melted and so readily combining with the pipe itself, which is of almost the same material, that the flame from prepared _tow_ blown to an intense heat by the _blow pipe_ is sufficient for the purpose. The rasp is used for filing the surface at the ends of the pipes where they are to be joined, and the _waxed rushes_ to try the joints in order to see that there is no escape of gas through some small hole. When the pipes are all laid and brought to their proper positions the fittings are fixed. Those which descend from the centres of ceilings are generally called chandeliers, and consist of a tube of metal fastened to the gas pipe, the end of which coming through the ceiling is furnished with an iron screw to fit the end of the tube. This tube is placed within a larger tube, from the bottom of which a still smaller one passes within the first. The gas therefore descends the tube from the ceiling, and enters the smallest tube, which communicates with the _burners_ that spring from the largest. The larger tube is intended to receive water, in which the end of the first tube rests, so that the gas is prevented from escaping, while by a nice adjustment of weights running over pulleys attached to the larger, the burners can be raised or lowered, as one tube slides within the other (_see large cut_). The _taps_ are placed at the burners to turn on or turn off the gas as it is required, and in order to fix and screw these, as well as to fasten joints in the fittings by means of _screw nuts_, the _pliers_ and the _wrench_ are used.

The _clamps_ are a sort of vice with grooved holes, for holding the taps and metal joints firmly while they are filed or otherwise prepared; the _drill stock_ is used for boring small pipes in order to make a branch to some other direction, and the _drill brace_ is intended for boring the main pipes, under which the large hooks are placed while a stock and bit attached to the upper screw makes the hole; the ordinary _braces_ are fitted to a _ratchet_ or cog wheel at one end, and are also used for making incisions by being worked backwards and forwards.

The several kinds of _burners_ are pierced or cut in such a way as to make the flame from the gas of different shapes, such as _fish tail_, _cock spur_, _star_, or _argand_, the names of which tell pretty well in what shape they appear. Small rooms are sometimes fitted with “telescopes” instead of chandeliers, the telescope being one tube sliding within another, and the space carefully filled with a properly adjusted cork or some other flexible and impervious substance. Bedrooms, and apartments where light is required at the walls or chimney pieces, are furnished with brackets, which either simply project from the wall, or are made with an arm moving on a ball and socket joint. The manufacture of the various portions of the apparatus used in gas fitting will be mostly found described under the trade of the Brassfounder.

MANUFACTURE OF GAS.

Very few of the readers of this book will remember the appearance presented by London streets before the introduction of gas; when all the thoroughfares were darker than even the commonest streets are now, and the only light emanated either from the shop windows or from dim oil lamps, which the rain or the wind would frequently put out, even when they did not burn out of themselves for want of being trimmed and replenished. A century ago these oil lamps were quite insufficient to light even the main streets, and people who walked out at night generally hired a “link boy” to light them as they went, with a great flambeau of hemp and pitch, which smoked and smelt insufferably. The nobility and gentlefolks who rode in carriages were also attended by footmen with flambeaux of a better sort, and outside the doors of some of the oldest houses in London there may still be seen the great iron extinguishers attached to the railings, where the torch-bearers put out their lights till it was time to escort their masters and mistresses home. The poet Gay, who wrote the celebrated fables, describes the link boys, and gives them rather a bad character for so often being connected with the bands of thieves and footpads which infested London streets, and robbed people with impunity in the dark. He says:—

“Though thou art tempted by the link man’s call,
Yet trust him not along the lonely wall;
In the midway he’ll quench the flaming brand,
And share the booty with the pilfering band.
Still keep the public streets, where oily rays,
Shot from the crystal lamp, o’erspread thy ways.”

Long before this, however, the inflammable nature of the vapour which streamed from burning coal had been observed by scientific men, and it was thought by many people that some method might be invented for making this gas useful for the purpose of lighting streets or houses. It had also been observed that the air suddenly escaping from the shafts of coal mines was often highly inflammable, and some experiments were made in the distillation of coal as early as 1726. In 1765 Lord Lonsdale proposed to the magistrates of Whitehaven to convey the gas from the neighbouring mines through pipes for lighting the town.

A number of eminent men afterwards made experiments with gas, but no decided practical result followed until a Mr. Murdock, of Cornwall, began to manufacture gas for lighting his house and offices at Redruth. In 1798 the same gentleman used gas for lighting the Soho Foundry, where four years afterwards a public exhibition of the new invention was made by means of an illumination to celebrate the proclamation of peace.

In 1803 a gentleman named Winsor first publicly showed at the Lyceum Theatre, in London, a system of illumination by gas, which was the commencement of our present method of lighting our streets and houses; and after great difficulties and various experiments, a company was formed for the purpose of carrying out the undertaking of superseding the old oil lamps and making use of the new invention. The premises of the company and their factory were situated in Pall Mall, where the Carlton Club now stands, and the lights first appeared from the corner of St. James’s Street to the Haymarket, while several jets were placed in front of Carlton House, the residence of the Prince Regent, afterwards George the Fourth.

By slow degrees, and by the assistance of Mr. Clegg, an eminent engineer, the manufacture of gas improved, and in 1814, when the allied sovereigns visited this country, and a general illumination was ordered, a magnificent pagoda in St. James’s Park was erected for the exhibition of the new light. The following year Guildhall was fitted with gas burners; and, although it had been predicted that the new invention would _ruin the navy_ by superseding the use of the oil brought by the whalers, and though some people declared that it was only a scheme for blowing up London, the success of these experiments led to its rapid adoption in most of the large towns of Europe.

It will now be necessary to say something of coal, of which more than 400,000 tons are used every year for the manufacture of gas in London alone.

The name coal was originally given to any substance used for fuel, and the use of mineral coal, or, as it was formerly termed, _sea-coal_, from the fact of its being brought by sea, has not prevailed for longer than 200 years. Coal is found in this country in extensive deposits called coal-fields, the most important of which are:—1. Those of the great northern district, including the coal-fields north of the river Trent. 2. Those of the central district, including the Leicester, Warwick, Stafford, and Shropshire coal-fields. 3. Those of the western districts in North Wales, South Wales, and Gloucester. The coal occurs in a number of layers, or beds, termed _seams_, and these are separated from each other by layers of slatey clay, called _shale_, and coarse, hard sandstone, known as _grit_.

The seams of coal are mostly comparatively thin, but varying from a few inches to six or eight feet in thickness, and underneath the layers is usually found a bed of mountain limestone extending beyond the coal-field, and rising to the surface of the ground around it.

The first process for finding coal is to bore with iron tools a perpendicular hole in the ground; then if coal is discovered, a shaft, or pit, from ten to fifteen feet in diameter, is sunk, and lined with brick, cast iron, or wood, to prevent the admission of water and the falling in of the sides. When the shaft reaches a seam of coal, passages are made, twelve to fourteen feet wide, and varying in height with the coal; from these proceed smaller ones, which are again crossed by large ones, enormous blocks of coal being left to support the earth above. As the mine becomes larger, a second shaft is sunk at some distance from the first, in order that air may be supplied to the mine, and that the gas that escapes from the coal may be carried away. A current of air is caused by burning a large fire in one shaft, and the draught is directed to the part of the mine where it is required, by doors, which close up some of the passages and leave others open.

There are several varieties of coal found in this country. The most important are: the common, or bituminous coal, which soils the fingers on handling; the cannel, or candle coal, which burns with a bright flame, but does not soil; the anthracite, or culm coal, which burns without flame, does not form cinder when half consumed, and is most useful for furnaces, in consequence of its intense heat and the absence of smoke. Although often classed amongst the minerals, coal is evidently of vegetable origin; many sorts of it being distinctly fibrous, and showing the grain of the wood from which it is composed. Upon examination with the microscope, coal shows vegetable remains; and these are frequently so perfect that they prove its formation from such plants as ferns and fir-trees, of a kind somewhat different from those which now exist.

The value of coal depends entirely upon its inflammable and combustible properties. It is used as the source of artificial warmth in our dwellings, and our manufactures are mainly dependent on it. Without coal there would scarcely be any working in iron, copper, lead, or other metals, as in populous countries the supply of wood is soon exhausted. Our potteries and our glass works are also carried on by its use, and the power of steam which moves all our great engines and machines is dependent on coal for its existence.

Great Britain produces more than one-half the coal that is consumed in the world, and about 180,000 persons are employed in obtaining it in our collieries.

The first process in the manufacture of gas is to subject the coal to a great heat, by which it is _carbonised_, or burnt until only the cinder, or coke, remains after the gas has flown off. This is done by placing the coal in retorts of fire-clay or iron, which are previously heated. These retorts, which occupy a building called the _retort house_, having been charged with coal, are perfectly closed, and the door _luted_, or stopped, with a sort of cement, so that the gas can only escape up the _ascension pipe_, the coke being left in the retort.

The gas from the coal then passes through the ascension pipe by what is called the _dip pipe_, into a main, a large horizontal tube extending along the length of the furnaces. This main is about half filled with water or tar, in which the ends of the dip pipes are immersed, so that as the gas runs in, it ascends through the liquid into the space above, but cannot flow back again into the dip pipes. In this way it is all collected in the upper part of the main pipe, and is ready for purification.

Where double retorts are used, each end is worked with at least three stokers, and an extra man for preparing the lids of the mouth-pieces. Others are required for extinguishing the coke, wheeling the coal into the retort house, clinkering furnaces, and attending to fires. Three stokers, assisted by a man to extinguish the coke, will perform all the work of taking off the lids, raking out the coke, extinguishing and wheeling it away from a bench of seven retorts, in twelve or thirteen minutes; they will then put the proper charge for each retort in the _scoop_, deliver its contents, and be ready for charging another bench in a further space of seven minutes, while a fourth workman will in the meantime have put on the lids, so that the whole work of discharging and charging the seven retorts will occupy barely twenty minutes.

This extreme dexterity is of course only acquired by long practice, and it must be admitted the labour is very severe; but this is moderated by the time the men have for repose between the charges. The first process in discharging or drawing is for one or two of the men to relieve the screws of the mouth-pieces of the retorts about to be discharged, by giving three or four rapid turns; another man instantly gives a knock to each of the cross bars to disengage them from the ears of the lid, and at the same time strikes the lid a blow with a piece of iron or hammer, in order to break the luting, and a light is immediately applied to prevent explosion, which would be likely to crack the retort if of clay. For want of this precaution, many lamentable accidents have happened through the gas exploding when combined with atmospheric air. The men then lift off the cross bar and screw of each retort, placing them on the ground, and then each seizes hold of a lid in both hands, lifting it by the projecting ears, and placing it aside to cool, ready for luting for another charge.

Three of the stokers then take up their _iron rakes_, which are simply rods of ¾-inch iron, about 12 feet long, having a handle at one end; the other end being turned at right angles is flat, about 6 inches long, 2 inches wide, and ½-inch thick. These are inserted in the retort, and the red-hot coke drawn to the mouth, whence it drops into the coke vault, where there is a man ready to extinguish by throwing water on it; or when there is no vault the coke drops into _iron barrows_ placed ready to receive it, and wheeled rapidly away when the charge is withdrawn. If the coke were not immediately extinguished it would smoulder, and the surface become covered with earthy ash, and detract from its appearance and value.

Formerly, in charging retorts, the operation being comparatively very protracted, there was a considerable loss of gas, in addition to the time and extra fatigue to the men. In order to remedy these inconveniences, a method has been contrived for depositing the whole charge in the retort at once; for this purpose an _iron scoop_ is used, this being a semi-cylinder of sheet iron, from 8 to 10 feet long and 10 or 12 inches diameter, with a cross handle at the end to assist in lifting and turning it round to empty the coals in the retort.

The charge of coal is placed in the scoop while it rests on the ground, having a bent rod underneath for the purpose of lifting it: one man takes hold of the cross handle, and two others lift the other end by the bent rod, and introduce it into the mouth of the retort. The scoop with its contents is then pushed forward to the further end, turned completely over, and immediately withdrawn, leaving the coal in the retort, which is raked into a layer of uniform thickness, when the lid, previously luted and ready, is placed in its position and screwed up as quickly as possible. The operation of charging a retort with the scoop does not occupy more than thirty or forty seconds, so that very little escape of gas can take place. The _shovel_ is used for lifting the coal to the scoop, the _clinking bat_ for breaking or removing the coke in the vault, the spud for a similar purpose.

The gas in the hydraulic main is of course very impure, having undergone no alteration since it came from the coal in the retort. It contains a quantity of tar and ammoniacal liquor in vapour, and these have to be separated from it and this can be effected by what is called condensation, the instrument used being known as a _condenser_. There are two or three forms of condensers in use, but a common one, which is represented in the engraving, is called the horizontal condenser, and is a rectangular box or chest formed of cast iron plates, put together with flanges, and perfectly tight joints. Its interior is provided with a series of iron trays, containing each about two inches in depth of water, and so arranged that the gas, entering at the bottom of the chest, passes in succession over the surface of the water in each tray, and traversing the whole length of trough ten or twelve times, passes off at the upper side. In the mean time a continuous stream of water enters at the top, and in its descent absorbs a portion of the ammonia, at the same time cooling and condensing the vapours in combination with the gas.

Horizontal condensers are sometimes composed of a series of pipes placed in a horizontal position, and immersed in water.

The other form of condenser, which is very generally employed, consists of a series of vertical pipes, connected in pairs by semicircular bends at top, and attached to a cast-iron box or chest at bottom. This chest has a series of divisions, the ends of which are sealed by liquid placed therein, so that the gas in its passage has to pass through the whole series of pipes. The pipes by their contact with the atmosphere radiate the heat acquired from the gas in its passage, and it being in consequence cooled, deposits the vapours as liquid in the form of tar, and water saturated with ammonia, generally called ammoniacal liquor. This condenser is sometimes used with an application of cold water on its exterior, in order to increase the cooling effect.

The other part of the purification is by a chemical process, in which a solution of lime is used to remove other impurities in the gas. This is called _wet lime purification_, or when the lime is only slackened (or moistened) it is called _dry lime purification_, and the process takes the sulphuretted hydrogen, the carbonic acid, and other matters from the gas before it is stored for use.

The wet lime purifier consists of a cast-iron cylinder entirely closed at top and bottom, except where the inlet and outlet pipes join it, and where an opening is required for charging it with lime-water, which same opening is also used for drawing off the charge. To the inside of the cover of this outer cylinder is bolted an inlet cylinder usually made of wrought-iron plate. This inlet cylinder is open at the lower part, and reaches to within a foot from the bottom of the outer cylinder, but has bolted to its lower flange a wide ring or dash plate of sheet iron, the outer diameter being only 8 or 9 inches less than that of the outer cylinder, so that a space of about 4 or 5 inches is left between the outside of the ring and the interior of the large cylinder.

The gas passes down through the inlet cylinder, and by its pressure forces its way up through the fluid lime, the surface of which is 8 or 9 inches above the dash plate.

The wet lime purifiers are variously worked; when four are used, two vessels are employed at one time, and when the lime in the first is incapable of absorbing the impurity, that purifier is put out of action, and the second and third are worked, and so on in succession.

When quick lime is slackened, reduced to powder, and slightly moistened with water, chemically this is called the hydrate of lime, and is often employed to absorb the sulphuretted hydrogen and carbonic acid from the gas. The process is termed dry lime purification.

Dry lime purifiers are generally rectangular cast-iron vessels, varying from 3 feet to 30 feet square, and from 3 feet to 4 feet 6 inches deep. Sometimes in small works they are made circular; this, however, is not very frequent, and is done for convenience or economy in construction. Each purifier contains a series of perforated shelves, trays, or sieves, supported by suitable bearers of wrought or cast iron, the ends of which are attached to “snuggs” cast on the purifier. In large apparatus there are also pillars placed at intermediate distances to carry the weight of the sieves and purifying material.

The upper part of the purifier is surrounded by a cistern or reservoir of from 6 inches to 24 inches deep, and from 3 inches to 6 inches wide, which is often cast with the purifier, and forms part of it, or at other times is attached thereto by bolts and cement, and is for the purpose of containing water to seal the cover. The cover of the purifier is of boiler plate or cast iron, the latter being preferable on account of its durability; but the increased weight is an impediment to its adoption. The rim or border of the cover is rather deeper than the cistern into which it is placed, and is effectually sealed by the water, so preventing the gas escaping from that point.

Often the purifier is divided into two compartments, so that the gas ascends through a set of sieves on the one side, and descends through another set on the other side, answering the purpose of two sets of apparatus. In all establishments, however small they may be, two distinct purifiers at least are necessary, to enable the impure lime to be removed from the one whilst the gas is being purified by the other.

The next subject for consideration is that of the _gasholders_, or vessels in which the gas is stored ready for delivery into the mains, which distribute it throughout the districts to be lighted. These vessels were originally termed _gasometers_, which name is sometimes even now applied to them; but as they have nothing whatever to do with the measurement of gas, but are mere vessels of capacity or stores, the simple name of gasholder is more expressive and appropriate.

The gasholder is composed of two distinct parts, one of which contains water, and is called the tank, the other is the vessel which contains the gas, being really the gasholder. On the Continent the former is very generally termed the “cistern,” and the latter the “bell.”

The tank is a large cylindrical vessel, constructed usually, for the sake of economy, of brickwork or masonry, but when the ground is marshy, or when water exists abundantly a short distance below the surface of the earth, which would prevent the construction in masonry at a moderate price, these tanks are made in cast-iron, and, indeed, in small works, are often of wrought iron. In the interior of the tank there are two vertical pipes for the admission and egress of the gas, called the inlet and outlet pipes; the former being in direct communication with the manufacturing apparatus, the latter with the mains which convey the gas to the town. These pipes rise a few inches above the level of the top of the tank, so that the water cannot overflow into them. A series of columns, generally of cast-iron, but sometimes of wood, or brick piers, are placed at equal distances around the tank for the purpose of guiding the holder.

The holder is a cylindrical vessel closed at the top, which is termed the roof, and open at the bottom, made of sheet iron, varying in thickness according to the dimensions of the apparatus, the smaller sizes being constructed of thin material in order to avoid an excess of pressure, whilst those of very large dimensions are made of stout plates for the purpose of obtaining sufficient pressure to expel the gas to the burners. The holder is somewhat less in diameter, but of the same depth as the tank in which it is placed, sometimes being partially suspended by chains which pass over grooved pulleys and counter-balance weights, but more frequently only guided by rollers attached around its lower and upper edges, which work against suitable guides in the tank and on the columns in such a manner as to permit the holder to ascend and descend in the tank with the greatest freedom.

The action of the gasholder is very simple. The tank being filled with water, and the holder immersed therein ready for use, there is a space between the surface of the water and the roof of the holder; the gas enters by the inlet pipe into this space, and with the force it acquires in being expelled from the coal, pressing on the surface of the water and underneath the roof, and over the whole area of both, causes the holder to rise. Thus, by its own force or pressure, the gas provides room for itself, and in proportion to the quantity entering so does the holder rise out of the water. For instance, a holder having 100 feet area, or about 11 feet 4 inches diameter, in rising 10 feet will receive 1,000 cubic feet of gas, and in descending, the same quantity would be expelled.

Gasholders, though often suspended, are never entirely counter-balanced, having always sufficient weight to give the necessary pressure for forcing the gas through the mains and smaller pipes to the burners, all through the neighbourhood which is supplied from it. The gasholder should be so constructed that, when it is full or at its greatest height, its lower edge will be so far under water as to prevent the gas from escaping.

The water in the tank serves three purposes; it is the means of resistance for the gas to lift the holder, it prevents the gas escaping or mixing with the atmosphere; and it is the means of expelling or forcing out the gas as the holder descends.

THE IRONFOUNDER.

Having already described the various operations of the trades employed in building and fitting a house, we will say something of the manufacture of those cast iron columns, girders, gratings, balconies, pipes, gutters, air traps, coal plates, stoves, and other articles which are so necessary to the Builder before his work can be completed. All these, as well as a great variety of other goods made in black or bronze iron, such as gates, bridges, pieces of furniture (like umbrella stands), iron taps, and even pots and frying pans, are made at the _Iron Foundry_.

Iron is a metal of a bluish gray colour; but in its pure state it looks almost white when polished, and has a brilliant lustre, while when it is broken the broken portion looks dull and fibrous. It is the hardest of all the malleable and ductile metals, and the most tenacious of all metals, an iron wire of ⅟₃₆th of an inch in diameter bearing a weight of 60 pounds.

In the pure state it requires the strongest heat of what is called a wind furnace to melt it.

Iron may be called the most precious of all metals; it is certainly the most beneficial to man, and its uses are innumerable; indeed, there is not a branch of human industry that could well afford to dispense with its aid and services; nearly all the tools, implements, instruments, and engines used by man are wholly or partly made of it, and we could better afford to give up all the other metals than to part with this, which is the most useful.

Iron is used in two different states, as _cast iron_ and _wrought iron_, the differences between them depending on the proportion of carbon combined with the metal, cast iron containing the most and wrought iron the least.

For the production of wrought iron in the ordinary way, two distinct sets of processes are required; first the extraction of the metal from the “ore” that is brought up from the mine, which metal is cast iron; and secondly the conversion of this cast iron into malleable or bar iron, by remelting, _puddling_, and _forging_. Bar iron is turned into steel by placing it in contact with charcoal in a peculiar kind of furnace.

When the ore is taken from the mine it is first burnt or calcined, and then removed to a blast furnace to be smelted. These blast furnaces are generally built of brick, and look like small towers. The ore is mixed with limestone, which causes it to melt more easily, and the fire is lighted with pit coal or coke. The melted metal sinks to the bottom of the furnace in consequence of its weight, while the limestone and dross float on the top, and are allowed to run off when they cool into a mass of what is called “slag.”

The melted metal is run off from the bottom of the furnace, either into moulds for some sort of castings, or into a large furrow made in a bed of sand. This large furrow has several smaller furrows on each side of it, and has received the name of the “sow;” the smaller furrows being called “pigs;”—and the iron when it is formed in this shape to be afterwards made malleable is called “pig iron.”

The pig iron is taken to other and smaller furnaces called puddling furnaces, the bottoms of which are lined with clay mixed with the slag just mentioned, and forming a substance which the puddlers call “bull-dog,” though it would be difficult to discover why it received that name.

About four hundred weight of the pigs is placed in the furnace, and as it melts the puddler stands at the furnace mouth with a long _iron rod_ bent at the end, and stirs it about, until it comes to resemble several great balls of iron paste. These balls are removed, and fall into iron trucks pushed along a small railway by boys, who wheel them at once to the “shingling hammer,” an immensely powerful hammer worked by steam, and this beats the iron into small square bars called “blooms.”

The blooms are next carried to the rolling mill, which is a pair of great rollers cut into grooves of various sizes, and between these grooves the bars are squeezed, as the rollers turn round, until they become much longer and narrower, when they are known as “forged bars.”

Some of the rolling mills, however, are plain cylinders without grooves, and when a slab of white-hot iron is placed between these it comes out from the pressure in a great broad sheet of metal.