a manufacture which ministers in no way to their | other half of the mould exactly fits by means of pins wants, but rather excites their disgust. There might and hollows which correspond in the two halves. have been something of this self-satisfied feeling

in the ancient Greek philosopher, who in passing through the fair at Athens, and seeing the shops filled with so large a variety of wares, exclaimed with a smile, "How many things are there that I do

Fig. 1692.

not want!" We too may smile at, and yet admire the The mould is next placed in an iron frame, Fig. 1693,

large amount of science, energy, capital, and skill

which are applied to meet a want as soon as it is generally expressed, or to gratify a whim or a caprice which may have become fashionable.

In the manufacture of tobacco-pipes there is much to admire. The pipe itself is an ingenious contrivance: the bowl is a kind of furnace in which tobacco is burnt; the chimney to this furnace is a long perforated stem, and the draught is excited by the lips of the smoker drawing air through the bowl: this supplies the ignited tobacco with fresh oxygen, and the products of combustion, consisting chiefly of nitrogen, carbonic acid, and oil of tobacco in a volatile form pass up the stem into the mouth of the smoker: the length of the stem cools the smoke, and deposits a considerable portion of the poisonous oil which is absorbed by the porous clay of the pipe, while the ashes, consisting of salts of potash, lime, &c., remain behind in the bowl. The comfort of the smoker is further consulted by the curve given to the stem, the effect of which in holding the pipe is always to maintain the bowl in its right position, while the small projection below the bowl serves as a guide in holding the pipe, or in passing the fingers down towards the heated part. There are many forms of clay pipe, but perhaps the best is that known as the old corporation pipe: it has a long stem, a large bowl, and a smooth surface, with a very slight yellow tint.

The clay employed in this manufacture occurs in the island of Purbeck in Dorsetshire, and in several parts of Europe, the lower portions of the deposits being most esteemed. The clay is carefully purified from foreign matters by some of the usual mechanical processes, and is formed into cubical masses of from 80 to 100 lb. each. From one such mass the moulder cuts off a number of lumps, each sufficient for one pipe, kneads them upon a table, and rolls them out nearly to the form and dimensions of the intended pipe, leaving a bulbous portion at the end for the bowl. When these rolls have become somewhat hardened by exposure to the air, they are bored by means of a wire mounted in a wooden handle: the man holds the roll between the three fingers and thumb of the left hand, and guides the wire very accurately by touch along the axis of the roll. The wire is slightly enlarged near the end, and this assists the operation. The roll thus impaled,

Fig. 1693

and its two parts are forced into close contact by means of nuts and screws. The clay of the stem is thus made to assume the form of the mould, together with any letters or ornaments which have been cut in the mould. The bowl is formed first roughly by the

Fig. 1694.

finger, and then by forcing into the mould the plug, Fig. 1694, which is held by its cross handle, while the rim determines the size of the cavity of the bowl. The bore of the stem is then continued until the wire touches the plug, but there is a small pellet of clay

which precedes the wire, and this requires to be removed by a little hook attached to the handle of a kind of knife, with which the pipe, now removed from the mould, is finished by cutting away superfluous morsels of clay, &c. The top rim of the bowl is finished by a small copper mould, Fig.

1695. Ornaments which are not given by the pipe mould are now added by means of small rollers and stamps. Roughnesses are rubbed away by a small grooved iron tool, and polish is given by grooved agates. The pipes are next arranged in shallow trays, and left for some time to dry.

Fig. 1695.

Notwithstanding the number of processes which each pipe has to go through, a good moulder will produce 500 pipes a day.

In baking the pipes they are arranged in crucibles or seggars of pipe clay, strengthened by the insertion of broken pipe stems. The bottoms are framed of these stems radiating towards the centre, and the interstices are plastered with clay. The top of each is dome shaped, and a pillar of clay is placed in the centre through the whole height, for the purpose of strengthening the crucible and also of supporting the stems of the pipes. Each crucible is provided with six horizontal ledges running round the interior at equal distances: these support the bowls of the pipes, Fig. 1691, is placed in the groove of one half of a while the central pillar supports the stems. See Fig. copper mould, Fig. 1692, slightly brushed with oil in 1696. As many as 50 gross of pipes can be arranged order that the stem may be smoothly delivered. The in one crucible. The crucibles are placed in a cylin

Fig. 1691.

drical kiln, Fig. 1696, with a circular fireplace at the | to polish the pipes by dipping them into a mixture of bottom. fat clay and water, and then polishing off with flannel. For the better kinds of pipes a sort of varnish is made by boiling soap, wax, and gum in water, and applying it by means of a flannel with friction.

Fig. 1696.

The bowls of tobacco pipes are also made of procelain, and highly ornamented. This is an example of pressed ware and of painting on porcelain, and calls for no special remark. Meerschaum pipes are noticed under MAGNESIUM.

SECTION V.-PREPARATION OF THE MATERIALS FOR
POTTERY AND PORCELAIN.

The pipes should be of a fine white colour after the firing, and such clay only is in general selected as will produce that colour. It happens, however, in certain localities that clay, in other respects of excelPure clay tempered with water forms a very plastic lent quality, be- paste, capable of being easily worked. It is exceedingly comes red in the firing, in consequence of the minute impressible, and assumes any form which the fingers portion of oxide of iron contained in it becoming of the potter may impart to it. The sensitiveness of converted into the red peroxide under the influence this material may be illustrated by stamping a seal of the oxidizing flame. The pipes come out of the upon a lump of clay, drying the lump and carefully kiln of a reddish hue. This defect has been reme-paring off all traces of the impression; if the lump be died in an ingenious manner by the deoxidizing influence of carbon; for which purpose the kiln, when in full action, has its chimney and all other openings closed for about three quarters of an hour, the effect of which is to condense the smoke of the fuel upon the pipes in the form of soot. The holes are then unstopped and the fire urged for a quarter of an hour, the effect of which is to raise the pipes to a red heat and burn off the soot or carbon. This operation is repeated several times according to experience, but the last time the fire is urged for an hour. The effect of this treatment is to convert the red peroxide of iron into the pale green protoxide, which scarcely interferes with the white lustre of the pipes, except just within the bowl, which remains slightly red.1

By a somewhat similar process an opposite result is obtained, viz. the production of black pipes. The seggars containing the pipes are partly filled with oak sawdust, and placed in the upper part of the kiln where the heat is least. The carbon of the wood thus combines with the clay, and as it is not burnt off by exposure to air at a high temperature, the pipes come out of the kiln of a dull black colour: they are polished by being dusted with plumbago and then rubbed hard with a cloth.

Baked clay has so strong an affinity for water [see ALUMINA], that when a new pipe is put into the mouth it absorbs the moisture from the lips, and adheres to the skin with such force that if suddenly detached it might tear away the skin. We have heard of such a case, and of a dangerous wound being produced thereby. The usual remedy is to tip the end of the pipe with sealing-wax, but a better plan is

(1) This method was communicated in 1730 by a manufacturer of St. Omer to Duhamel du Monceau, whose treatise on the manuMétiers," of the Academy of Sciences has served as the text for most writers on this subject up to the present day. It is some encouragement to the Editor to pursue his laborious task, when

facture of pipes written for the celebrated treatises on "Arts et

he finds such men as Réaumur and Duhamel devoting their time and splendid talents to the preparation of elaborate treatises on the Useful Arts.

now passed through the kiln the impression of the seal will be revived, thus showing that the molecules of the clay had received and retained the impression to a considerable depth below the surfaces.

But this sensitive plasticity of clay, which so admirably adapts it to the shaping of vessels and other articles, leads to some inconvenience in the firing; for the clay undergoes so large an amount of contraction by heat that thin wares become distorted, and are also liable to crack. And this distortion is not altogether due to contraction or to the unequal evaporation of the water: it is also occasioned by the tendency of the aluminous particles to return to their normal position, from which they were slightly disturbed in the process of throwing or turning on the potter's wheel. In this process the clay is spun upon a vertical lathe, and moulded by the pressure of the hand into continuous bands, spirally disposed, passing from right to left, from the base of the vessel to the summit. When such a vessed is raised to a high temperature the particles thus disturbed and the points thus compressed tend to return back to their normal position of equilibrium, as may be easily proved by marking upon the vessel, before it is fired, two points in a vertical line, when it will be found after the firing that these two points are no longer in the same vertical: the lower point will have moved more towards the right than the other, and this is so well known to the workmen, that on attaching handles to cups, jugs, &c., before the firing, they are accustomed to place them a little askew, and the distortion produced by the contraction in firing restores them to their vertical position.

This remarkable plasticity of clay is lowered down by the addition of a substance which does not possess that property in the slightest degree, viz. silica. This substance is prepared from flints, quartzose sands, felspar, &c., but these are not the only nonplastic materials employed; for chalk, sulphate of baryta and calcined bones are used with good effect.

In the manufacture of earthenware two principal ingredients are employed, clay and flint. The nature GG 2

The preparation of these materials involves many processes and much labour and care. The first process is the mixing of the clay, and is called blanging. The proper proportions of blue and white clay are placed overnight in a trough about two and a half feet deep, with the needful quantity of pure water. In the morning these are well incorporated with the water by means of a long blade of ashwood with a cross handle at its upper extremity, called a blunger or plunger. This is worked violently in the trough until a smooth pulp is obtained, a pint of which is, by the addition of water, made to weigh 24

and proportions of these rest with the manufacturer, | rent enamel," which gives transparency to the parand upon the soundness of his judgment in these celain according to the quantity used. respects, more than in any peculiar art of construction, depends the excellence of his ware. The clays commonly used in the Staffordshire potteries are brought from Devonshire and Dorsetshire, brown and blue clays from the latter, black and cracking clays from the former. The black clay owes its colour to the presence of bitumen or coaly matter, but this disappears in passing through the potter's oven, so that the wares formed of it are nearly white. Cracking clay is valuable for its pure white colour, but is liable to crack during the first burning, and must therefore be mixed with other clays which have not this tendency. Brown clay is also liable to an imperfection called crazing or cracking of the glaze. Blue clay is the best for ordinary purposes; it will bear a larger proportion of flint than the others, and therefore produces a whiter ware. For the finer kinds of earthenware, a fifth variety, being the china clay of Cornwall, is largely employed. This consists of felspar, one of the ingredients of granite, in a partially decomposed state. It is collected in the following manner :-The stone is first broken up with a pick-axe, and thrown into a stream of running water. This washes off the argillaceous parts, and keeps them suspended while the quartz and the mica (the other two ingredients of granite) sink at once to the bottom. At the end of these rivulets the water is dammed up, forming what are called catchpools, and here the pure clay subsides in a solid mass, which is afterwards dug out in blocks, (the water being drawn off,) and laid on connected series of strong shelves, called linnees, to dry. It is then crushed, packed in casks, and sent to the potteries as china clay. In this state it is a white impalpable powder, consisting of 60 parts alumina, and 20 silica. A certain proportion of undecomposed felspar is often added, as it serves to bind the ingredients more closely together. Neither clay, flint, nor lime can be melted separately in the greatest heat of a porcelain furnace, yet when mixed together in proper proportions one mineral acts as a flux to the others, and the mass can be fused without difficulty. Flints for the manufacture are obtained from the chalk districts, chiefly of Gravesend and Newhaven. They are white externally, but dark and clear within. When the fracture exhibits yellow spots, the flint must be rejected as containing iron which would stain the ware. Steatite or soapstone occasionally forms one of the ingredients in the manufacture of porcelain.

There is a mineral called pegmatite, in which all the materials for hard porcelain exist ready mixed. Pegmatite consists of felspar, kaolin, and a small quantity of prismatic quartz, the last being valuable for the whiteness and transparency which it imparts. Therefore a good pegmatite, well decomposed, is all that the manufacturer requires. Soft porcelain, as it is manufactured at the present day, consists of two ingredients from the mineral kingdom, and one from the animal kingdom, viz. kaolin, Cornish stone, and bones. The last melt into "a sort of semi-transpa

Fig. 1697.

BLUNGING.

ounces, but when china-clay is used, a pint is made to weigh 26 ounces. To facilitate the blunging process, the clay is sometimes pugged in a cast-iron cylinder, 4 feet deep and 20 inches in diameter, through the centre of which runs an upright shaft furnished with a spiral line of knives inclining downwards. A corresponding series of knives is fixed to the inside of the cylinder, so that as the shaft revolves the knives cut up the clay, and by their inclination force it downwards. In its divided state it then passes through an opening in the bottom of the cylinder, whence it is removed to a vat, mixed with water, and blunged by means of a perpendicular shaft furnished with cross-arms. During the revolution of the shaft, the finer particles of the clay mix with the water, and the stony substances which may be present sink to the bottom.

The preparation of the flints involves several processes. They are first burnt in a kiln for about 30 hours, and either thrown into cold water while red-hot (which greatly increases their brittleness), or allowed to cool before being taken out. They are next placed on a strong iron grating, and acted upon by powerful stampers, or wooden beams shod with iron, Fig. 1698. These reduce the flints into fragments sufficiently small to pass through the grating. These fragments are conveyed to the flint-pan, Fig. 1699, consisting of a strong circular vat, 10 or 12 feet in diameter, the bottom of which is formed of quartz or felspar in small blocks, imbedded in mortar of a similar composition to the material which is to be