of the powder to be sifted which passes through the muslin. The only advantages which this utensil has over those in common use consist in its superior cleanliness, and in the ease with which light powders may be brushed out of it.

C are crucibles both open and covered.-Those made with Wedgwood's fire ware are for some purposes preferable to any others.

D is an air-tight jar with a lid applicable to many useful purposes. 4 is a ledge running round the inside of the jar. 5 is a trough round the outside of the jar to receive the lid. When the lid is put on, the trough is to be filled with mercury, oil, water, or putty, in order to make the whole air-tight. 6 is the cover with holes to receive tubes if necessary, or they may be closed by earthen stoppers.

E an adapting tube of earthenware useful for many purposes in a laboratory.

Ga galvanic trough of queen's ware for experiments in Voltaic electricity.

P a pneumatic trough of earthenware with a shelf, &c. of the usual construction.

R an earthenware retort of the usual form.

PLATE XIX.

Is the representation of crown glass in its various states from the time it is taken out of the furnace until it becomes a perfect circular sheet of window glass. The whole is fully explained in the Essay, page 195.

PLATE XX.

Apparatus for the preparation of oxymuriate of soda, oxymuriate of magnesia, &c. for the use of calico-printers.

A is the furnace for heating the materials which furnish the oxymuriatic gas.

B a cast-iron vessel containing water, and forming a waterbath for the reception of the still marked C.

C the body of the still, which should be made of lead, and properly adapted both in form and size to the cast-iron waterbath in which it stands. dd are water lutes for the top of the still to drop into; a convenient contrivance for keeping the apparatus tight, and preventing the gas from escaping into the atmosphere.

E the top or head of the still, made of lead, and sufficiently large to allow of its dipping six inches into the gutter of wate

which surrounds the still. By this simple contrivance the head can be put on or taken off at pleasure and without difficulty. f f f are pipes and lutes for the different parts of the apparatus.

G G is a stirrer, with a square frame of wood covered with lead, attached to it for the purpose of agitating the materials within the still.

Ha bent funnel passing through the cover of the still, for pouring in the diluted sulphuric acid.

I is a small intermediate vessel, partly filled with water, and designed to arrest any uncombined muriatic acid which may occasionally arise from the still during the process.

K represents the large receiver of lead charged with the alkaline solution... This prepared liquor is intended to receive and absorb all the oxymuriatic acid gas that comes from the still, and when sufficiently saturated it is drawn off by the cock N for use.

L is an opening for filling the reservoir, occasionally cleansing it out, &c.

M M M the agitator for constantly stirring the alkaline solution, and which is necessary to promote the absorption of the gas. In large works this is moved by a power from the steam engine..

N is the cock for drawing off the finished liquor as mentioned above.

The glass bottle, which appears in the same plate, contains two bubbles of glass; one is seen at bottom, the other floating on the surface of the liquor. This is recommended as a small and useful apparatus for ascertaining the specific gravity of the oxymuriate of soda. Its advantages, together with the mode of using it, are fully described in Vol. I. page 236.

PLATE XXI.

Is descriptive of an apparatus for bleaching cotton goods. Fig. 1 is a section of the bucking apparatus, which may be thus described.

A is the boiler for heating the alkaline lye.

B represents a very large wooden vessel in which the calicoes are placed.

C the cock and pipe, by means of which the hot lye is conveyed upon the goods.

D is a square box designed for spreading the lye over the calicoes within the vessel B.

E a pump for raising the liquor again out of the vessel B, from whence it is conveyed by the spout I back into the boiler A. F is the furuace for heating the lye.

G represents the false bottom of the calico vessel, full of holes for the passage of the lye when it has run through the goods under operation.

H is a round wooden staff which completely fits a hole at the bottom of the bucking vessel. It is called a duck, and is intended to be pulled up whenever it is designed to run off the spent alkaline liquor.

I is the spout for conveying the liquor back to the boiler as above mentioned. In some houses the boiler is fixed below the bucking vessel, and the pump is placed within the boiler as described in page 271.

Fig. 2 is the representation of a common whale-boiler.

A is a metallic boiler to be fixed in brick-work, similar to that in fig. 1.

BB is the top part of wood, called a crib, with the bottom full of holes. In this the calicoes are placed one above another, often amounting to many hundred pieces at one operation.

C is the pipe through which the lyes boil up, and d d is the umbrella suspended over the pipe for the purpose of spreading the lyes more effectually as they fall down again upon the goods.

This apparatus for bleaching possesses several advantages. The perforated wooden vessel preserves the calicoes from being injured by coming in contact with the boiler, while the pressure occasioned by so great a weight of goods frequently increases the temperature of the lye by some degrees higher than it would acquire in an open vessel, and this additional heat has a powerful effect in bleaching. By this contrivance there is no necessity for pumping; for, so long as the lye in the vessel A actually boils, a constant stream will flow through the pipe C upon the goods in B, and thus a perpetual circulation may be kept up till the goods have attained the desired whiteness.

PLATE XXII.

Is descriptive of some peculiar modes of purifying water. Figs. 1, 2, and 3, represent a glass apparatus invented by Mr. Pepys for filtering small quantities of water or other fluid, and may be thus described.

Fig. 2 is a glass vessel with a rib of tinned iron going round the inside of it near the top. This rib has many notches upon it, and these are designed for receiving a number of small glass rods as shown in the drawing, fig. 1. These are intended for supporting a sheet of filtering paper or any other kind of filter which may be placed within the jar. When this vessel is charged with the liquor proposed to be filtrated, the cover d, which

1

completely fits it, is put on to preserve the contents from dust or other accidental impurities.

Fig. 3 is a glass vessel for receiving the fluid as it filtrates from No. 2; therefore, when the apparatus is to be used, the two vessels are adapted to each other, the parts marked a and b being accurately ground to fit; and when put together, the whole, except the top, has the appearance as shown at fig. 1. This apparatus is sold by Messrs. Knight, of Foster Lane, the price 17. 11s. 6d. to 21. 2s. each, according to their size, &c.

Fig. 4 is a section of an improved water reservoir, fitted up some time ago on a large scale in Scotland.

A is a flexible pipe of leather for the purpose of allowing the tube B to alter its position according to the height of the water within the reservoir.

B is a metallic tube with a rose-head, to allow of the passage of water, and yet prevent the entrance of impurities which might accidentally float upon its surface.

C is a hollow ball of copper swimming on the water for the purpose of keeping the rose-head always near the surface, in order that no water may be ever drawn but what comes from the surface of the reservoir.

DE is a wooden trough for carrying off the waste water, and preventing the overflow of the reservoir.

F is a large iron pipe for conveying the water from the spring into the trough G, firmly fixed within the reservoir.

For the advantages of this peculiar construction of a water tank, see pages 374 and 394, &c.

PLATE XXIII.

This is a plan of a convenient apparatus first employed at Paris for the production of sal-ammoniac.

A A are two furnaces for decomposing common salt, each 14 feet long by 7 feet 6 inches wide.

BBBB are pipes of bricks, each 2 feet wide, which go through the wall dividing the workshops, and conduct the vapours of muriatic acid gas into the chamber C.

C is the leaden chamber where the muriatic acid gas and the ammoniacal gas meet for the production of muriate of ammonia, or sal-ammoniac.

DD are flues belonging to the two furnaces A A for carrying off the smoke of the fire-places. These are 14 inches by 24 inches each, and are carried up together, and at last united into one chimney above the top of the building.

EE are pipes belonging to the two furnaces A, each 14 inches wide, connected with the chimneys, and designed for

carrying off the muriatic acid gas by that conveyance into the atmosphere, when the furnaces are used for the production of soda without making sal-ammoniac.

F F are cast-iron plates or dampers, which open or shut the communication of the pipes E with the chimneys at pleasure. G G are similar iron dampers which cut off or determine the passage of the muriatic acid gas into the leaden chamber C. H is a ground plan of the kiln for burning the animal matters designed to produce ammonia.

J a leaden pipe to convey the ammoniacal gas into the chamber C.

K is a hole through the arch or superior part of the kiln, which is designed to receive an eolipile from whence the steam of hot water is forced into the chamber C, at the same moment when the acid and alkaline gases are entering the same receptacle.

M the kiln chimney.

N is a flight of steps leading to the ash-pan.

O a pipe by which the chamber is emptied of the liquid muriate of ammonia when necessary.

P a flight of steps leading under the chamber C.

Q a door to enter into the said chamber.

The peculiar advantage of this apparatus is, that while the muriatic acid gas is passing into the chamber C, at that moment another stream of ammoniacal gas is entering the same chamber from the kiln H, which occasions a mutual condensation and prevents any loss. For further particulars see page 453 of this volume.

PLATE XXIV.

This plate contains two representations of Mr. Lucas's furnace for converting cast-iron cutlery to good steel cutlery. Fig. 1 is a front view of the furnace complete.

B B are cast-iron bearers for supporting the grate bars. D foundation wall below the floor of the work-shop for supporting the interior of the furnace.

E E the two fire-places for heating the furnace. 2 is the dome or arch of the furnace. 3 3 the internal side of the front wall, in which is an aperture 4, by which the workman enters to place the iron cylinders holding the goods. This being done, the aperture is walled up as shown in the engraving, except two holes left in the bottom of the wall marked 5 5.

H is the chimney for conveying away the smoke of the fireplaces.

Fig. 2 is a perpendicular section of the same furnace, presenting a side view of its internal parts, and showing how the