fragments, and the whole together forms a paste. When the manufacturer wishes to obtain "cold-drawn" oil, he at once exposes this pasty mass to the action of the

sluice is opened, and the seed is drawn out into a number of oblong flannel bags, as shown in the cut. In more modern contrivances the seed is heated by steam, instead of by a charcoal fire; but in both cases the seed is kept constantly stirred while being heated, and is drawn out when heated into the bags which contain it while undergoing pressure.

In one of the buildings is a range of hydraulic presses capable of exerting an immense pressure. The bags of seed are flattened slightly with the hand, and piled up one on another in cast-iron cases, which are placed in the press as here sketched. The force is then laid

[Grinding the Linseed.]

press, by which oil of very fine quality, but in very Jimited quantity, is obtained. To obtain the main supply, the paste is heated before being exposed to the press. The heating is effected in different modes in different mills. In some cases there is a small fire-place situated in the corner of the building, and heated by burning charcoal. The seed is contained in a circular copper pan, which is set over the fire, and a stirrer is so adjusted as to keep the seed in motion while being heated. When the seed is sufficiently heated, a door or

[Crushed Linseed falling into bags.]

[Bags of Linseed in the Hydraulic Press.]

on, and in a few seconds we see the oil oozing from every pore in the bags, and running down into.convenient receptacles beneath. When as much oil is obtained by this pressure as the seed in this form will yield, the pressure is removed, the bags are taken out, and then stripped off the seed, which has by this time assumed the form of a flat, hard, solid cake. This cake is again ground, again heated, and again pressed, by which a further portion of oil is extracted from it.

When the bags are for the last time stripped from the seed (an operation which is facilitated by a simple piece of apparatus sketched in the next cut), the latter present almost the hardness and solidity of a board. They are trimmed and brought into a regular form fit for packing, and are then sold as oil-cake. This cake is a valuable article to agriculturists, and has at times been sold at a high price; it is employed in the fattening of cattle, sheep, and other animals, for which it seems fitted by the oil which it still contains, and which could not be wholly removed by pressure. It is usually given to the animal mixed with some other sort of food, such as hay or cut chaff. On the Continent linseed-cake is sometimes given in a liquid state, being diffused in hot water, and given to the animals to drink, hay and other food being given at the same time. Much controversy has arisen among agriculturists and graziers as to the precise value of this kind of fattening food, in reference both to the condition of the animals when fed on it, and the manure resulting from the system ; but the result seems to be very much influenced by the price at which the cake can be purchased.

[Stripping the Bag from the Oil-cake.] When the cake is so dry as not to leave enough nourishment for fattening cattle, it is occasionally used as manure; in which case the cake is reduced to powder, and is sown by hand on ground intended for wheat, barley, or turnips; being harrowed in with the seed, and used at the rate of from three to six quarters per acre. It is rape-cake that is thus used, linseed-cake being generally too costly.

The oil, as expressed from the seed, requires very little more attention. It is transferred from the vessels into which it falls, into casks and other receptacles, and is then ready to be applied to some one or other of the numerous purposes for which it is fitted. It is principally as a vehicle for mixing oil-paints that it is used; but there are innumerable branches of the manufacturing arts in which it is extensively employed. Many medicinal preparations, too, derive a portion of their value from the presence of this oil, in a more or less refined or purified state. Linseed-oil, in its usual form, is essentially what is termed a "fat" or unctuous cil, possessing a property which renders it very slow in drying. To remedy this, which for some purposes would be a great inconvenience, a small portion of the oil made is converted into "drying" oil, whose distinctive quality is indicated by its name. The drying quality is imparted to the oil by boiling it with sugar of lead, white vitriol, red lead, or some one of a rather numerous list of substances. Common drying oil is often made by boiling linseed-oil with red lead; but the finest kinds are produced by some finer agent, sometimes one or other of the gums.

One department of this mill is devoted to the preparation of turpentine in the form which it usually assumes in the manufacturing arts. The common turpentine of commerce is imported into this country chiefly from Canada and the United States, in barrels or casks. When these barrels are opened, the turpentine appears as a stiff, adhesive, honey-like paste, midway between the solid and the fluid state. It consists of two very different component parts: a clear transparent liquid, which forms the " oil of turpentine," or "essence of turpentine," of commerce; and a yellowish or brownish solid, forming common resin; and it is the object of the turpentine-distillery carried on at these works to separate these two component ingredients.

In one of the buildings is a large still, together with numerous vessels, and other apparatus, having for object the separation of the liquid from the solid components. Most readers are probably aware that in all processes of distillation the substance to be distilled is exposed to heat in a close vessel, and raised to such a temperature as will vaporize some of the component ingredients without affecting the others, and thus separating one from another. In the common distillation of spirit, for example, a fermented liquor, called "wash," is exposed to such a heat that the spirituous or alcoholic portion is caused to rise into vapour, leaving the greater part of the water and nearly all the other ingredients behind; and by the subsequent condensation of this vapour, liquid spirit is obtained. So it is with turpentine. The liquid or spirituous portion vaporizes at a much lower temperature than the solid or resinous; and therefore, while the resin settles at the bottom of the still in a solid form, the spirit rises in the form of vapour, and passes through a refrigerator or cooling-vessel, whereby it is brought to the liquid form. The temperature to which the still is raised, and the general arrangement of the apparatus, depend on the nature of the substance to be distilled, and are among the minuter objects of the manufacturer's skill. The "black" resin and the "yellow" resin of the shops are produced in the same way, but from different kinds of turpentine.

Starch-Factory.

We may extend our visit a little further east, and devote a few paragraphs to a notice of the operations carried on at a starch-factory in North Shields. The building is neither so large nor the operations so complex as in many instances which have engaged our attention; but the chemical transformations connected with this branch of manufacture are interesting, and deserve a little study.

Starch is a peculiar component part of vegetable substances, bearing a curious relation to sugar and to alcohol. Starch, sugar, alcohol or spirit, and vinegar, are all composed pretty much of the same ingredients; and by the processes of malting, mashing, distillation, and acetification, the same grain of corn may be made to yield any one of these very different products. We here speak of starch from grain, but it exists in many different kinds of vegetables. For instance, it exists in the seeds of nearly all kinds of corn; in tap-roots; in potatoes and other tuberose roots; in the stems of palm-trees, and many other kinds of plants; and in many species of lichen. The nature of the starch itself is not less remarkable than the diversity of the sources whence it may be obtained; it is always mixed with other chemical principles, from which it is separated when required to be used simply as starch. It consists of very small roundish white granules, which are generally lodged in the cells of the cellular tissue. These granules differ in size, often in the same seed or plant, being smallest near the circumference of the containing plant. Each granule consists of a membrane, often beautifully marked, and containing a transparent colourless material resembling gum. The membrane is insoluble in cold water, but is soluble at a temperature of about 160° Fahr.

Starch and gluten form the two main ingredients in the flour or meal of which bread and pastry are made; and it happens fittingly that the kind which is best suited for making bread is not that which is most appropriate for starch. Pure starch, though a jellylike substance when mixed with water, is rather indigestible; and flour which contains a large proportion of starch in relation to the gluten is not well fitted for making bread. The best bread is made of flour which contains the greatest proportion of gluten; and the

quality of bread is apt to be varying from the circumstance that the relative proportions of starch and gluten differ not only in the different kinds of corn, but in the same species or variety, according to the season when they are sown, or the manure which has been applied to the land. Sir Humphry Davy found that in spring-grown wheat, one hundred parts yielded seventy of starch to twenty-four of gluten; while autumn-grown wheat yielded seventy-seven of starch to nineteen of gluten. It has been observed by a practical agriculturist, that "were a scientific system of agriculture to prevail in this country, one kind of wheat, treated with proper manure, would be raised and sold exclusively to the starch-manufacturer; while another kind, treated with its proper manures, would be raised for and sold only to the baker.

Rice is very rich in starch, in comparison with the gluten which it contains. It is said that Carolina rice is more abundantly supplied with it than any other grain, insomuch that there is not more than three or four per cent. of gluten with it. That potatoes contain starch may be made readily visible by the following simple process :-Rasp or grate a potato to fragments over a sieve; pass a current of water over the raspings, and this water will pass through the meshes of the sieve in a milky state; let the water remain stationary some time, and a starchy deposit (more or less mixed with other bodies) will appear at the bottom of the vessel. The combination of gluten with the starch in flour is not recognisable by the eye, but the separating of the two may be very readily effected by the following method:- -Make up a stiffish paste of flour and water; leave it at rest for a time; and then carefully and gently knead it between the fingers, while a current of water is flowing on it; the water will wash away the starchy particles, leaving behind a tenacious elastic substance which constitutes gluten.

For the practical purposes of commerce, starch is generally prepared from wheat, and there are different modes of proceeding, one of which is as follows:The grain, sifted clean, is steeped in water until it becomes swollen and soft; after removal from this water, it is immersed in clear warmish water, and then put into bags, which bags are exposed to strong pressure. This pressure forces out the starchy particles into water; and the water being removed and replaced by clean, still more of the milky liquid is prepared, and the moistened grain loses pretty nearly all its starch. Instead of the pressure, the grain is sometimes crushed under vertical grindstones, or between rollers, and the starch washed out from the fragments. The milky liquor, by whichever method obtained, is poured into large cisterns, where it is allowed to settle and deposit its starch. The surface-liquor is poured off, new water added and stirred up with the starch, a second settlement allowed, a second removal of the surface-liquor, and so on several times, until nearly all the foreign ingredients, such as gluten, sugar, gum, and albumen, are washed out and separated from the starch. After the final deposition of sediment, there appears on the surface a thin layer of gluten and albumen, called slimes,' which is removed, and used for feeding pigs or oxen. The starch beneath is in layers or strata of different quality, the particles first deposited being purer than those at the surface; and by a dextrous contrivance these different qualities are removed one by one, and permanently separated. After being again mixed with water and passed through a fine sieve, the starch is laid on linen cloths in wicker baskets, where it is allowed to dry gradually. The solid starch is then cut into pieces, and placed in a warm room or stove to dry.

wheat is first crushed between iron rollers, and steeped in as much water as will cover it. Being thus allowed to remain several days, the mixture ferments, and the starchy particles by degrees fall to the bottom. After a subsequent fermentation in another vessel, the starch is separated by a sieve from the bran with which it had become mixed, and is afterwards allowed to settle for several hours in square frames or cisterns. The surface water is let off through taps or cocks in the side of the vessel; the 'slimes,' or thin mixture of gluten and albumen, is removed; the washing with water and the deposition of sediment are again repeated, and the same series goes over two or three times. After this the starch receives the blue colour which most kinds present, by having a small quantity of smalt mixed up with it. The starch is then transferred to oblong wooden boxes or trays, which are pierced with holes and lined with thin canvas. these boxes it remains to drain and solidify, and is afterwards turned out in a solid compact form. The mass of starch is broken or cut up into pieces four or five inches square, and the pieces are placed upon a flooring of very absorbent bricks, where they very soon dry. The drying in a stove, the scraping of the pieces with a knife, the packing in paper, and the final drying of these packages, complete the series of operations.

In

There are many modifications of the processes, followed by different persons and in different places; but in all of them the separation of the starch from the other component parts of the grain is brought about by pressure, bruising, or rubbing, aided subsequently by fermentation, washing, straining, and drying. There is a "patent starch" made of Indian corn, and many other varieties of starch, for which the credit of more or less excellence is obtained; sometimes it is a new kind of seed or root which is brought into use for this purpose; sometimes a new modification of the process of manufacture; at other times a new arrangement of apparatus; but the broad principles are pretty much alike in all. As a further example, we may notice the mode of making potato-starch for sale. The potatoes, after being well washed in a cylindrical cage, are brought to the state of a pulp by means of a rasping-machine, consisting of a roughened hoop or cylinder so placed as to grind the potatoes to fragments while it is revolving. The pulp (which is wetted while being rasped) falls into a vessel beneath; and with a machine worked by two men, two or three tons of potatoes may be reduced to pulp in a day. This pulp, by washing, stirring, settling, drying, &c., is made to yield its starch, which, by a well-managed process, amounts in quantity to from fifteen to twenty per cent. of the weight of the potatoes used.

Some of the calico-printers use a kind of stiffening material or starch, which they call British gum, and which was brought into use on account of the high price of gum-Senegal. This British gum is prepared from wheat-flour, and is a kind of medium between common starch and common flour-paste.

6

A starch-factory is one of the least inviting to a mere visitor; for almost the only processes to be seen are conducted in buildings full of vessels containing the sours,' or fermenting mixtures of starch and water, in various stages of progress. The odour is anything but agreeable; and unless the looker-on can find something to interest him in contemplating the chemical changes involved in the process, his stay would probably not be a long one. Starch, however, is a material rather extensively used in the arts, besides the well-known domestic purpose to which it is applied; and its production is certainly worth a pass

CURIOSITIES OF BRITISH NATURAL

HISTORY.

CENTIPEDES AND MILLEPEDES.

THE group at the head of the present article presents us with an association of creeping things, from which many turn with indifference, if not disgust, but which are nevertheless far from being destitute of interest. It must be confessed indeed that they are neither striking in their appearance nor obtrusive in their habits; they are creatures of darkness, and conceal themselves from observation. It is during the gloom and silence of night

"When the dew is on the grass, And the wisp on the morass," that they come forth from their lurking-places, and wander abroad in search of food; but with the dawn of day they seek the obscurity of their retreats. These

No. 803.

creatures constitute a group termed by naturalists Myriapoda, the first order of insects according to M. Latreille, but really forming a distinct section or class, of the subkingdom articulata, and displaying affinities to the crustacea, scorpions, and insects, yet distinguished by characters of their own. They are composed of a series of distinct segments, and to every segment is appropriated one pair of limbs; sometimes indeed two pairs.

The head is furnished with jaws, antennæ, which are regarded as feelers, and eyes either simple or compound. Respiration is effected through spiracles, as in insects, whence air-tubes ramify over the internal viscera. Like insects, they undergo a metamorphosis, or rather several changes before acquiring their perfect form; and the sexes are distinct.

Their movements are winding and serpentine; some are slow, gliding gently along; others, on the contrary, are active and rapid in the extreme. They feed on

VOL. XIII.-3 D

decayed vegetable and animal substances, on fruits, roots, &c., and many on living prey.

The Myriapoda resolve themselves into two distinct tribes, one represented by the Millepede, the other by the Centipede. The first, Chilognatha, Latreille, the genus Julus of Linnæus, comprising the Millepedes, is characterized by the cylindrical form of the whole body; the antennæ are composed of seven joints; the first segment of the body, sometimes the second, is the largest, and presents the appearance of a corslet or little buckler. It is not until the fourth year in some, the fifth or sixth in others, that the pair of limbs on the several segments become doubled, and that maturity is attained. They live upon decayed animal and vegetable substances, and are found under stones, in the ground, at the foot of old walls, in the fissures and under the bark of time-worn trees. If we take the Millepede as an example of this tribe, we observe it to be elongated and cylindrical in form, divided into rings or segments, and capable of rolling itself up spirally into a ball. The segments are from forty to fifty in number, smooth, horny, and convex above. Each segment in the perfect animal is furnished with two pairs of short legs (certain segments excepted), by means of which the animal appears to glide along, without any effort, the legs being almost invisible as we look down upon the moving creature. The respiratory orifices or stigmata are placed on the sternal (or lower) aspect of each segment, and lead to a double series of aerating sacculi, whence tubes emerge, to be distributed on the internal organs. In addition to these breathing orifices a series of pores runs down each side of the body, exuding an acid secretion of unpleasant odour.

to the fifth take place from the month of March, the time when the eggs are hatched, to the end of July or beginning of August.

Whether these changes are as precise as stated, we think a matter of doubt. At all events we have recently examined and sketched a female Julus of considerable size, with forty-six rings, and eighty-two legs on each side. The first segment after the head had a pair of limbs on each side, that is a double pair altogether; between the first and second segment appeared a distinct orifice; and then appeared only one limb on each side; to this succeeded two limbs on each side for every segment, excepting the. three caudal segments, which were destitute of limbs.

The common Millepede (Julus terrestriș) is too well known to need description; it lives in light vegetable mould in gardens or plantations, under old walls, stones, logs of wood, and the like: it feeds on vegetable matters. Our European Millepedes are all of small size; there is, however, a species found in Brazil, the Julus maximus, Linn., of the length of seven inches.

Certain millepedes are separated from the genus Julus, in consequence of the form of the segments, which are not only less convex, but their outer margin is reflected up, and forms a projection with a point at its posterior angle. They are of small size, and found in damp places in the earth: they form the genus Polydesmus of Latreille. To those in which the eyes are apparent, Dr. Leach gave the name of Craspedosoma. The Polydesmus complanatus (Julus complanatus, Linn.) is by no means uncommon in gardens. It is more active in its movements than the com:non millepede, and is capable of rolling itself up.

Another genus is termed Glomeris by Latreille. The species have much resemblance to the woodlouse (oniscus), or rather the Armadillo Woodlouse (Arma

The female millepede deposits her eggs, which are very minute, in the earth or in the earthy powder of decayed wood, which is in fact a rich vegetable mould. We have said that the young undergo a series of transmutations before arriving at their perfect development. The progress of these changes has been watched by De Geer, Savi, and other zoologists, and are too remarkable to be passed by unnoticed. The young when first hatched are very minute, utterly destitute of limbs, quite smooth, and of a kidney shape, but of course so minute as to require a lens for examination. In the course of a few days afterwards they undergo a sort of moult, changing the skin, and then appear divided into about eight segments; a pair of simple eyes appears on the head, which is furnished also with two antennæ; the three segments following the head have each a pair of limbs. In a few days a second moult takes place, the body is enlarged, the number of segments increased, and the number of limbs augmented to seven pairs, one pair on each segment succeeding the head. At the age of a month, or thereabouts, a third change takes place, and the millepede appears with twenty-two segments and twentysix pairs of feet, but of these the anterior eighteen pairs only are used in progression. The general form and aspect now approximates to that of the adult. Some time now elapses before the fourth moult, which gives thirty-six pairs of legs. Subsequently the male acquires thirty-nine rings, and the female sixty-four, with two pairs of limbs to every segment. But after this, two years elapse before the perfect development and maturity of the animal is completed.

Such is a summary of the observations recorded, to which it may be added, that the changes from the first

power of rolling themselves up into a ball, like the Armadillo, with which indeed they are often confounded by superficial observers; insomuch that from the comparison of actual specimens, we have drawn out the most palpable differences, to serve as a guide to young inquirers. In Glomeris, taking the Pill Millepede as our example, the limbs are small, and arise from a median abdominal line; they are short and numerous, and do not appear laterally beyond the jointed carapace or backplate.

In Armadillo (an Isopodous Crustacean, as is also the common Woodlouse) the limbs are large, proceed from the sides of the abdomen, and extend beyond the back plate, excepting the hind pair. In the Pill Millepede (Glomeris) the head is larger and more concealed, the antennæ are short and end club-shaped.

In the Armadillo Woodlouse the antennæ are longer and filiform or pointed.

In the Pill Millepede the shelly covering is firm; in the Armadillo much softer, as in Oniscus. The terminal segment of Glomeris is large, of Armadillo small and triangular. In the latter the lateral edge of the dorsal armour along each side is serrated, in the former continuous.

The Glomeris, or Pill Millepede, is black, with yellow margins to the rings or segments. Armadillo is yellowish-grey clouded with brown, or brown with yellow blotches; it exceeds the Pill Millepede in size. Both are common, and roll themselves up in the form of balls, and were formerly used in medicine. A species of Armadillo from Italy (A. officinalis) was employed on the Continent. The Pill Millepede, Glomeris marginata, Leach (Julus ovalis, Linnæus), is found under stones and amongst moss, and in the same situations as the common Millepede. Both the Pill Millepede and the Armadillo Woodlouse are abundant