to be to afford greater space for the passage of the warp threads, as the sheeds open, or pass each other, than is afforded in the ordinary kind of healds employed for the weaving of fine fabrics.

It is proposed to make the loops of the healds double, that is, passing over the shafts at top and bottom, and meeting both at the back and front; and also that the headles shall be formed by long and short loops alternately; that is, one of the upper loops being long, and the lower loop connected to it, short, the next upper loop is to be short, and its lower loop long, and so on alternately. By these means, the knots of the one series of loops, will be a little distance above the knots of the other series of loops, and the warp threads passed between these knots will be depressed as the heald descends, by the upper series of knots, and raised as the heald ascends by the lower series of knots for the passage of the shuttle between them; the threads being thereby enabled to pass each other with greater freedom, and of consequence less friction, the space for the warp being open in the middle.

Healds are usually made of woollen or hempen cord, twisted very hard, and called heald or headle yard; these improved healds may be made of the same material, or they may be fine wires, which in some cases would perhaps be preferable.

Account of a patent granted to JOHN FREDERICK SMITH, of Dunstan Hill, Chesterfield, in the County of Derby, Esq. for his Invention of Improvements in the process of Drawing, Roving, Spinning, and Doubling Wool, Cotton, and other fibrous substances.

THE patentee has discovered that it is very desirable, in the processes of roving, spinning, and doubling of wool, cotton, and other fibrous substances, to prevent, as much as possible, the fibres of the material being disturbed, or drawn out of the positions in which they were first placed by the carding engine; and in consequence of this discovery, it is directed that in all the future operations to which the fibrous materials may be subjected, whether of roving, spinning, or doubling, that the fibres should be carried through the several engines in the same direction, that is, always beginning with the end which was first delivered, or wound in the preceding machine; and this is the invention of improvements in the processes of roving, &c. which constitutes the subject of this patent.

The instructions of the patentee, in carrying this invention into effect are, that the operator should observe carefully which end of the sliver first came from the carding engine, and of consequence to introduce that end first into the roving machine, and continue to observe the same direction of the fibres in all the subsequent stages of operations, that is, spinning, &c. And here it is to be observed, that if the rovings are conducted into cans, which is sometimes the case, that then, cans with their two ends open are to be used, because by

the employment of these cans, the ends of the rovings which were first delivered, may be readily got at. And when the rovings are to be wound upon bobbins, it is desirable to employ the new invented bobbins with moveable ends, for the capability which those bobbins possess of enabling the cop to be slidden off its barrel, will likewise afford the means of getting at the interior of the cop, for the purpose of finding the end of the roving first wound upon the bobbin, that the spinning may commence from that end.

This mode of proceeding, the patentee considers, cannot fail of producing a much more smooth and even yarn, or thread, than could be effected by the ordinary mode of roving and spinning. [lb.

Self-generating Gas Lamp.

(From the Edinburgh Philosophical Journal.)

H

B

E

THE Oil vessel of this lamp is répresented at A. B is the tube by which the oil is admitted; C is the generator; D is a hollow vessel, where the heat from the burners F, underneath, is collected; the dotted lines are projecting ridges on it, within the generator, to prevent the oil running down and collecting at the bottom of the generator. E is a circular piece of iron, to collect and retain the heat. G are tubes to conduct the gas from C to F. L is a tube to supply the vacancy in A with gas, as the oil is discharged into C. I is a metal heater to fit into D.

To use the lamp, fill A partially with oil, alcohol, or any fluid from which gas is produced, and having made the metal-heater H red-hot, place it in the bulb D; after it has continued in it a minute or two, turn the stop cock I, allowing the fluid to drop slowly on the heated bulb D, below, by which it will be converted into When it is found to escape

gas.

in sufficient quantities from the burners at F, set it on fire, remove the heater, and a beautiful bright flame will be supported by its own heat as long as there is oil in A.

It may be found necessary to replace the first heater by a second, when the lamp is used for the first time, to expel more effectually the atmospheric air from the generator and tubes. The heat collected in D will be found sufficient to generate gas to a third burner,

if required, as it is an indisputable fact, that most bodies, in a state of combustion, give out much more heat than is requisite to support an equal body of flame, and this is quite evident, by fire spreading so rapidly in all combustible substances, if not checked.

ON GILDING.

GILDING UPON BRONZE.

Continued from p. 592, vol. 4.

7th. On giving the colour of Or Moulu.-When it is desired to give to gilt articles the colour of or moulu, the scratch brush is used less freely than usual; the work is then restored, by heating it more highly than when it is to be left mat, and it is afterwards allowed to cool a little. The or moulu colouring, is a mixture of blood stone, alum, and common salt; these are diluted with vinegar, and applied with a pencil, over the surface of the gilding, taking care to avoid the parts to be burnished: the piece is then placed upon lighted charcoal, which may be rendered more active by gently blowing it; the heating is continued until the work begins to assume a black colour. The piece should be sufficiently hot to cause water sprinkled upon it to be rapidly converted into vapour. The article is then withdrawn from the fire, and plunged into cold water; it is to be well washed, and the orange colour which the gilding presents, is equalized by rubbing the piece with a pencil dipped in vinegar, if the surface be smooth, or with weak nitric acid, if it has been ornamented with the graver, or the chisel. In either case, the article is to be well washed, and dried at a moderate fire.

8th. On producing the colour of red gold.-When the gilding is to receive the colour which distinguishes the triple alloy of gold, silver, and copper, usually employed in the manufacture of jewellery, this is effected by the subjoined operation.

The work, when sufficiently gilt, is, whilst warm from the fire, to have a fine iron wire attached to it, and is immersed in, or covered with, the composition known under the name of gilding wax; this is made of yellow wax, red ochre, verdigris and alum: when thus prepared, it is heated strongly over a charcoal fire, and the inflammation of this covering of wax is promoted, by throwing some small pieces of the same substance into the fire: the work must be turned about on the fire so as to heat, and burn off the wax on every part at the same time; when the whole of the gilding wax is burned off, and the flaming has ceased, the piece is to be plunged into water and well washed and scratch brushed; using pure vinegar in the operation. If the colour is not good, and the tint equal throughout, the piece should be covered with a solution of verdigris in vinegar, dried on a gentle fire, again washed in water, and scratch brushed with vinegar; should the colour be too dark, a little weak nitric acid, may be used, instead of the vinegar. After being coloured, the work is to be washed, burnished, again washed, wiped with soft linen, and dried by a gentle heat.

In performing the foregoing process, the utmost care is necessary VOL. V.-No. 1.-JANUARY, 1828.—5

to avoid the deleterious effects of the mercurial, and other fumes. Great numbers have fallen early victims to this business, or after a few years devoted to it, have been rendered impotent for the remainder of their lives. To obviate these fatal effects, M. D'Arcet has devised such arrangements in the forges and furnaces used in the large manufactories, as cause them completely to carry off the vapours, without exposing the workmen to their action. In the Dictionnaire Technologique, there are drawings of the plan and elevation of such an establishment, where the business is to be carried on very extensively; these we have not thought it necessary to give, as, with us, gilding is only an occasional business. It is of high importance, however, to avoid the mercurial vapour, even in a single operation, especially when large pieces are to be gilt. For this purpose the forge chimney should have a strong draft, the air for which may be supplied by tubes leading to the outside of the building, which may be regulated at pleasure, whilst that from doors and windows is irregular, and if admitted in sufficient quantity, would frequently render the workshops uncomfortable.

M. D'Arcet advises the gilders not to touch the mercury with the naked hands, when it can be avoided; and to wear gloves of leather, or of bladder, or, which is best, of waxed silk. Before leaving the workshop, and especially before eating, the hands and the mouth should be carefully washed with warm water, and afterwards with soap and water, to completely remove the amalgam, and the nitric solution.

GILDING ON IRON AND POLISHED STEEL.

Guyton de Morveau has pointed out a very easy manner of gilding, durably, upon iron and steel, after they have been polished. The following is his process. Gold, rolled very thin, is dissolved to saturation in nitro-muriatic acid (aqua regia;) upon this is poured a quantity of ether, equal in volume to the quantity of acid employed. The whole should be placed in a flask of double the capacity of the two liquids; it is to be well stopped and strongly shaken, when the ether will take up the gold, which the acid had dissolved, and will be found swimming upon it, exhibiting a beautiful yellow colour. This liquid is to be separated from the acid by means of a funnel with a very small opening; the acid being the heaviest may be allowed to flow out first, and at the instant the ether begins to follow it, the receiving vessel must be changed. The liquid must be carefully stopped, and preserved for use.

When any piece of iron or steel is to be gilt, it must be first well polished, and slightly warmed, the auriferous ether may then be applied with a pencil, the ether will quickly evaporate, and leave the gold, which may be firmly fixed with a burnisher.

GILDING BY HEAT, WITH leaf gold.

The metal intended to be gilt, whether iron, copper, or brass, is first made smooth with a scraper, and burnished. It is then placed on the fire, and heated, until, if it be iron, or steel, it acquires a blue colour; and to an equal degree, if it be copper or brass; a piece of

gold leaf is then applied on the part to be gilt, and gently rubbed down with the burnisher; the work is again placed upon a moderate fire, to restore it to the former temperature. Several coats of leaf may be thus applied, successively; each coat is formed of a single leaf for ordinary work, and of two leaves for finer articles. The work is placed on the fire, and the gold burnished on for each coat, and the burnishing is continued on the last, until the metal is cold.

COLD GILDING ON METAL.

Dissolve about 60 grains of fine gold, rolled very thin, and ten or twelve of pure copper, in two ounces of nitro-muriatic acid (aqua regia.) When the solution is complete, it is to be poured, drop by drop, upon clean linen rags, sufficient in bulk to absorb the whole of the liquid; these are to be dried, and then placed upon a china plate, and reduced to cinders, taking care in lighting them not to use a sulphur match. These cinders, of course, contain the gold in fine powder.

When a piece of metal is to be gilt with this powder, it must be prepared by being left with a clean surface, such as is given by a fine stone, or charcoal; a small pad of linen is to be slightly moistened, and dipped into the box containing the powder; with this the work is to be rubbed, until its surface is sufficiently covered with gold. Large articles are afterwards burnished with blood stone burnishers, and smaller ones with those of steel, using soap suds, to prevent scratching, or stripping the gold.

GILDING THE EDGES OF BOOKS.

Equal parts of Armenian bole, and of sugar candy, are to be well rubbed together in a dry state; a portion of well beaten white of egg is then added, and the whole carefully incorporated. The book to be gilt is placed in the cutting press, its edges smoothly cut, and polished; a light coat of white of egg is then passed over it, and allowed to dry, after which the same is to be done with the composition above described; when this latter is perfectly dry, it is to be rubbed smooth and polished; it is then ready to receive the gold. To apply this, the prepared edges of the leaves are to be moistened by means of a hair pencil, dipped in clean water, and the gold immediately laid on. The burnishing is effected by rubbing the gold, when dry, with a dog's tooth, or agate burnisher.

GILDING ON THE COVERS OF BOOKS.

When the binding of books is completed, a portion of well beaten white of egg is passed over those parts which are to be gilt, in a similar way to that described in the preceding article; this operation, however, may be dispensed with: the gold is then laid on, and fixed in its place by what are called binders tools, which are made of brass, and have the intended ornaments engraved upon them, in relief. These tools are to be heated and pressed upon the leaf, and wherever they have touched, the gold will adhere firmly. The superfluous gold is then rubbed off with a piece of cotton wool, which is to be preserved, and burnt, to obtain the gold from it.