tribute the flame in a sheet equally over the whole of its surface. The other portion of the heat is conveyed by many parallel or diverging horizontal flues, under and across the floor or hearth of the oven, to the middle or partition wall, over the surface of which is distributed equally the flame and heat which ascends from the numerous flues in immediate contact with the wall. This sheet of flame ascending, strikes the spring or shoulder of the arch, and is reverberated upon the saggers beneath, until it meets the reverberated flame from the opposite of the arch, and both escape by the vents at the summit of the oven; the same construction is also applied to the opposite chamber. For some purposes but one chamber is used, and the number of furnaces is varied as the magnitude of the oven may require. In some cases, the fuel is burnt upon an iron grate or bars in the furnaces; and in others, the fuel is laid upon the ground without any ash-pit. The method of constructing the improved oven, with all the peculiarities of the flues, is exhibited in Plate XV., in which a, represents the square walls or body of the oven; b, the partition wall; c, the furnaces, with their iron bars; d, the mouths of the furnaces, by which the fuel is supplied; f, the ash-pits; g, the horizontal flues, under the hearth of the oven; h, the vertical flues; i, the vents in the summit of the arches; k, the entrances to the chambers of the oven.

The patentee claims, Firstly,-conveying the heat by horizontal or diverging flues, and distributing it equally over the inside of the chambers of potters' ovens, by the means before described; and, Secondly, reverberating the heat after it has crossed the floor of the oven and ascended the opposite wall, by means of the arch, before it escapes by the central vent; he also claims the exclusive right of applying the same mode of construction for the conveying and distributing of heat in single ovens; that is to say, ovens with one chamber only, without any partition wall.-[Inrolled in the Inrolment Office, February, 1843.]

To ANTOINE BLANC, of Paris, in the Kingdom of France, merchant, and THEOPHILE GERVAIS BAZILLE, of Rouen, in the same Kingdom, merchant, now residing at Sablionere's Hotel, Leicester-square, in the county of Middlesex, for certain improvements in the manufacturing or producing soda and other articles obtained by or from the decomposition of common salt or chloride of sodium,being a communication.-[Sealed 12th February, 1840.]

THIS improved process consists in decomposing sea-salt, by silica and water, under the influence of a strong heat. The action of silica on sea-salt, under the influence of water and heat, is a fact which has been long known in chemical science, but hitherto no application has been made of it, upon a large scale, in the arts for the manufacture of soda.

When in the laboratory an intimate mixture is made of sea-salt and sand, and when that mixture is exposed to the action of a cherry-red heat, in a large porcelain tube, a decomposition of the mass takes place, when the vapour of water is made to pass over it, and there results a neutral silicate of soda, insoluble in water, while hydrochloric or muriatic acid is disengaged, and may be received or condensed in water. The vapour of water, in decomposing, transforms the mass into a proportion, more or less considerable, of silicate of soda, at the extremity of the porcelain tube, to which a tube of glass may be adapted, destined to conduct the acid gas into a vessel full of distilled water. After some hours of ignition, the liquor becomes strongly acid, and this liquid muriatic acid is not colored in the least yellow, as the acid of commerce usually is by the presence

of iron.

The mass withdrawn from the tube is to be lixiviated, to carry off all the undecomposed sea-salt, and the remainder is to be mixed with a little carbonate of soda. This mixture being fused in a crucible, forms a vitrified mass, consisting of a sub-silicate of soda, soluble in water. The sub-salt is to be dissolved in water, and transformed into carbonate of soda and gelatinous silica, as follows:A stream of carbonic acid gas is passed through the so

lution, whereby white flakes of silica are deposited, and there remains, in solution, only carbonate of soda, which may be evaporated and calcined, and disposed of as dry soda, or soda-ash, or formed into crystals. Upon a large scale, the transformation of sea-salt into neutral silicate of soda, may be conveniently performed, as follows:-The calcination of sea-salt and siliceous sand may be made in cast-iron cylinders, placed in furnaces, so that the flame may pass around them and raise them to a cherry-red heat. The arrangement of these cylinders may be the same as those of gas retorts. The axis of each cylinder is occupied by a large tube, of the same length as the cylinder; which tube is pierced with a multitude of holes; this tube is inserted at one end of each cylinder, and into the other end of each cylinder a large porcelain, stone-ware, or glass tube, is adapted, through which the muriatic gas is allowed to pass off. Each cylinder is to be filled loosely, by very moderate pressure, with an intimate mixture of sea-salt and sand; and when the mass has arrived at a cherry-red heat, the steam of water is made to pass from a steamboiler into the perforated tube, which traverses the cylinder. For the due success of the operation the workman, charged with its management, should allow the steam to pass very slowly and equally into the tube; for if too much steam were introduced into the tube, the iron cylinder might be forcibly expanded, and lose its shape; in fact, the steam should not be admitted so quickly as to lower the temperature of the mixture beneath a cherry-red heat; when this is attended to, the water is decomposed in the apparatus, and the transformation of sea-salt and sand into neutral silicate of soda goes on without risk, and in a complete manner.

The proportions of the materials to be employed, to obtain a good decomposition, are sea-salt 280 parts, and sand 200 parts.

As muriatic or hydrocholoric acid has a certain value in commerce, and as in certain localities large quantities are employed, especially for the manufacture of chlorine, it is frequently important to collect this gas instead of allowing it to pass off by the chimney. The tube adapted to the

cylinder, for the disengagement of the acid gas, should be very large, especially at its orifice, for otherwise it might be choked up by volatilized sea-salt. The tube that carries off the gas is to enter first of all into a large empty chamber, into which the volatilized salt may be condensed and deposited. This chamber is to communicate with a large cistern of wood or stone, having its bottom covered with water. By this arrangement and by employing sufficiently large vessels, the acid gas may be collected with little or no pressure, while the apparatus of Woulfe, usually employed in the preparation of muriatic acid, requires a series of twenty or thirty bottles, and considerable pressure.

Before proceeding to the transformation of the neutral silicate into sub-silicate, the mass is to be lixiviated, as above stated, in order to extract the undecomposed portion of sea-salt. The neutral silicate of soda, obtained in this first operation, being insoluble, it must be rendered a soluble sub-salt by combining it with an additional proportion of soda; sixty parts of carbonate of soda must be employed to convert one hundred parts of neutral silicate into sub-silicate of soda. There is, however, no inconvenience in employing a little excess of carbonate, as this salt is not liable to be decomposed by heat, and remains always in the solution. The apparatus destined to calcine this mixture is either an ordinary reverberatory furnace, or a large Hessian crucible. At a cherry-red heat the vitrification takes place, and the matter in this state is soluble in hot water. The insoluble silicate, however, may be employed in the manufacture of glass, with suitable additions of lime and alumina.

The vitrified sub-silicate of soda ought to be pulverized and thrown into hot water to effect its solution. This solution may be made in large wooden or stone reservoirs.

The process adopted by the patentee for obtaining carbonic acid, consists in extracting it from lime-stone by calcination in continuously acting lime-kilns. To the limekiln, a dome-top is adapted, furnished with a tube that passes into the vessels or vessel containing the solution of sub-silicate. The sub-silicate of soda is decomposed in

this operation; carbonate of soda being formed, which remains in solution, and gelatinous silica being deposited, the operation is finished whenever the carbonic acid ceases to be absorbed by the solution. This silicic acid may be obtained as a white jelly when the carbonic acid is free from smoke, in which state it is well adapted for the manufacture of fine glass. Care must be taken not to employ too great a number of vessels in effecting the transformation of sub-silicate of soda into carbonate, because in that case the pressure would be too considerable, and would obstruct the flow of air through the lime-kiln, and the proper calcination of the lime.

With this view, the patentees prefer employing a single vessel of very large capacity, as the operation goes on perfectly well, and the draught of the furnace is sufficiently great to maintain uninterrupted combustion to the end of the process. [Inrolled in the Petty Bag Office, August,

1840.]

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Specification drawn by Messrs. Newton and Son.

To SAMUEL DOTCHIN, of Myrtle-street, Hoxton, jeweller, for improvements in paving, or covering and constructing roads, ways, and other surfaces,-being a communication from his son, lately deceased.-[Sealed 8th October, 1842.]

THESE improvements consist in paving roads, &c., with blocks of wood, or other suitable material, of the peculiar form represented in Plate XIV. Fig. 1, is a side view, and fig. 2, a plan of the block; the latter figure being encompassed by a circle, to shew that it may be cut out of a circular block or piece of timber. The improved block consists of six sides, and an upper and lower surface; the sides are all equal, but, instead of being formed perpendicular to the upper and lower surfaces, they incline alternately in opposite directions. The advantages to be

derived from this form are, that each block will be supported by three of the adjoining blocks, and will also support three, as shewn at fig. 3, which is a plan of part of