resulting from the separation of the gas, thereby considerably reducing the labour of the stoker, or attendant of the fire. Secondly, in affording a simple and ready means of spreading the coal over the retort, in a thin uniform stratum, thereby equalizing the temperature of the coal throughout, rendering the luting of the joints unnecessary, and causing a speedy separation of the gaseous products; the whole operation requiring but ten minutes. The purifying vessels adopted by the patentee are of two different constructions, but both are in principle, somewhat similar to a Woulf's Distillatory Apparatus; in them, the gas is made to pass successively, through several vessels, charged with lime or other purifying materials, and the chemical action which takes place from the contact of the gas, produces a constant agitation, without the necessity of resorting, as usual, to mechanical aid.

Fig. 1 shows a longitudinal section of a retort, supposed to be placed in the furnace, occupying the space between the two dotted lines a a; the two ends of the retort are flanched on to the body, and projecting beyond the brickwork, are removed from the influence of the fire. b and c are two scrapers, with long rods attached to them, which pass through the flanched ends of the retort, and have cross handles at their extremities; as the scrapers have to be pushed the whole length of the retort, the rods should be about a foot longer than the latter; as this proportional length is not shown in the engraving, they are exhibited as broken off near to the handles. The form of the scraper b is shown by the separate figure 2, and the form of c by the separate figure 3; in each of them are two square notches, which sliding upon square bars of iron placed longitudinally on the upper side of the interior of the retorts, are thereby suspended to it, and kept uniformly in their proper positions.

The process of working the retort is as follows:-Previous to charging it, the scraper c is drawn outwards from the body of the retort close up to the end, and the scraper bis pushed inwards so as to come in contact with c; both scrapers being then beyond the opening d, the charge of coals is admitted through the latter, by opening the cover e, which may turn upon a hinge joint, or be lifted up by means of a pulley and counter weight. The scraper c is then. drawn back from its recent situation (beyond d,) which spreads the coals out in an even layer, all over the bottom of that part of the retort exposed to the action of the fire. About a foot from each scraper, the rods are connected by a solid and hollow screw, so that when the rods are drawn out, they may be removed out of the way by unscrewing them at those parts. As the distillation of the coal ceeds, the gas escapes by the tube f, and from thence to the purifying vessels. When all the gas has been separated from one charge of coals, the scraper c is thrust forward, pushing before it and clearing out all the coke, which falls into the coke-box g, previously closed by the mouth-piece h; from this receptacle, the coke may be afterwards let to fall into a barrow, and be wheeled away.

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As it necessary that the apertures for the admission of the coal, and the discharge of the coke, should be closed air-tight; the paten

tee has availed himself of the distant, or screened, situation of these parts from the heat of the furnace, to adapt a lining of lead to the covers, by which means they are closed as effectually as by the troublesome process of luting the joints at every charge. To recharge the retort, both the scrapers are again thrust back beyond the opening d, when a similar quantity of coals is admitted, which are spread out again in an even layer, by drawing back the scraper b, and the distillation re-commences. The process is in this manner repeated as long as the production of gas may be required.

It should be noticed, that the ends are connected to the body of the retorts by flanches screwed together, so that when the furnace has destroyed the latter, a new one may be screwed on to the ends of the old retort, at a comparatively little cost, instead of having them wholly new. From each end of the retort, a tube projects horizontally, about ten inches long, and one inch in the bore, which serves both as a support, and a guide, for the seraper rod which slides through it.

Fig. 4 gives an external view of that end of the retort where the coke is discharged, and fig. 5 a similar view of the other end of the same, where the coals are received: the letters have reference to the like parts in each of the figures.

The purifying vessels proposed by the patentee, are of two descriptions; we have selected that for our engraving which we consider to be the best, but shall give some account of the other.

Fig. 6 gives a vertical section of a series of three vessels, i j k, the lower parts of which, up to the dotted line l, are occupied with a stratum of lime, or other purifying material. The impure gas from the retort is first received into the tube m, and by its pressure descending along the bent arm, it passes out of the expanded, or bellmouthed, end, where it mixes with the lime in the vessel i, and deposits therein much of its impurity, by condensation; from this vessel, the gas again rises and enters the tube n, from thence, filtering through the lime in the vessel j, it re-ascends, and enters by the tube o, into the third filtering vessel k. The pressure upon the gas being constant, the filtration may be repeated through any number of these vessels, but the extent of the process already described will, in general, be sufficient to produce gas of great purity; in which case it would be conducted by the tuber to the gas-holder, for subsequent distribution.

The three covered tubes p p p, above the filtering vessels, are for the purpose of charging them with the lime; the dotted circles are perforations in the sides of the vessels (furnished with plugs,) for ascertaining the depth of the stratum of lime, &c.; and the three tubes qqq at the bottoms of the vessels, are for discharging the lime when saturated with the various matters that have been condensed during the process of filtration. To aid the complete discharge or clearing of these vessels of their contents, three bars of iron are employed as scrapers, one in each vessel, and nearly of the same length; a rod, as a handle, is screwed into each, which passes through a hole (provided with a stuffing box) in the side of each vessel.

VOL. V.-No. 1.—JANUARY, 1827.-3

The other form of purifying vessels, proposed by the patentee, will, perhaps, be understood by the following description. A large cylindrical basin is divided internally by a series of circular partitions, placed concentrically; on the bottom of the whole, the stratum of lime, or other matter, is laid. Over these partitions are placed in an inverted position, a number of circular vessels one within another, and arranged alternately between the partitions, with their edges imbedded in the layer of lime. The gas, which enters by a tube through the centre of the bottom of the larger exterior vessel, first ascends over the innermost partition, and thence descending by the interposition of the bottom of the innermost inverted vessel, it is compelled to enter the first portion of the stratum of lime; having filtrated through this, it passes up between the outside of the inverted vessel and the next partition; passing over this, it descends on the other side of the last-mentioned, and enters a fresh portion of lime; and so on, from compartment to compartment, until the purification of the gas is completed, when it is conducted into the holder ready for the purposes of illumination.

GAS AND VAPOUR ENGINES.

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Some remarks upon explosion and vapour engines. By the EDITOR.

Ir is now upwards of three years, since Mr. Samuel Brown's gas engine was introduced to public attention; and from the ingenuity of its construction, and the sanguine expectations of the projector, and some of his friends, it excited an unusual degree of interest. The principle of its action was by no means novel, the production of a partial vacuum by the combination of explosive mixtures of atmospheric and inflammable air, had been long spoken of, as a substitute for that power obtained by steam. In the year 1814, a model of an engine acting upon this principle, was placed in the hands of the Editor, with a view to his instituting some experiments with it. The inflammable gas to supply it, was to be obtained from the charring of wood; and it was imagined, that the charcoal produced, would go far in defraying the expense of working it. The model was rudely made, but appeared to work with considerable power, and the subject would have been pursued, but for the removal of the Editor to Virginia, on which account the model was returned to the inventor, and it is believed that no further effort was made to perfect it, and thus, the time and money which would probably have been uselessly expended upon it, were saved.

Since that period, several attempts have been made to apply the same principle, either by using inflammable gases, or the vapour from fluids which are volatile, and combustible; hitherto, however, these efforts have been unsuccessful, and we have strong doubts, whether under any ordinary circumstances, an engine operated upon by an explosive mixture of gas, or vapour, will ever be constructed, which will successfully compete with the steam engine.

The want of success, which has attended the ingenious and perse

vering efforts of Mr. Brown, renders it less necessary to urge our objections, than it would have been two or three years ago. There does not appear, in the successive attempts to perfect this engine, any deficiency of genius, perseverance, or funds; and yet, so far, we believe, it must be pronounced to be a failure. One of the main difficulties which has been experienced, has arisen from the large quantity of gas consumed, which has, to an enormous extent, exceeded the calculations originally made; such at least is the information which we have received, and that, from sources entitled to credit.

Having in our possession an engraving of Mr. Brown's engine, as constructed by him in the year 1824, and as we are not aware that its structure has been exhibited in any of our Journals, or in any other work published here, excepting Nicholson's Operative Mechanic, we have determined to insert the engraving, and description, which we doubt not will be acceptable to our readers. We have spoken of this engine as a failure; we ought, however, to state, that such is not the opinion of the inventor: an engine upon Mr. Brown's principle has recently been constructed in this city, by his son, who came from England for that purpose, under the patronage of one of our most respectable fellow citizens. This engine, although not actually completed, is so far so, as to have been set in operation; the question of its value, in the form it has now assumed, will, therefore, soon be settled. Mr. Morey is also here, with the design of completing one of his explosive engines, an account of which we formerly published. This, in its structure, differs considerably from Brown's; it has two cylinders with pistons; these cylinders are alternately filled with air, and vapour from heated spirits of turpentine; this mixture when ignited by a taper, explodes, expelling nearly all the air through an opening in the bottom of the cylinder, which bottom is formed of leather, in such a way that it operates as a large valve, allowing free exit to the heated and expanded air, and closing so as to prevent its return; the pressure of the atmosphere operates upon each piston, alternately, as it would in an ordinary atmospheric engine with two cylinders.

Engines, analogous in principle to the ordinary steam engine, but acted upon by the elastic force of vapour from different volatile liquids, have also been constructed, or proposed; and several patents have been obtained for them. The objections to these, appear to us to be insuperable; for although there is no theoretical obstacle in the way of their operation, the practical difficulties which present themselves, have hitherto caused, and are likely to insure, the abandonment of all such attempts; whenever we meet with accounts of such in the journals, we expect the same fate to attend them, which we know await those numerous advertised improvements which sin against the established laws of nature; not that we esteem them alike absurd; alcohol, ether, quicksilver, or any other volatile fluid, may be used to work an engine; the attempt, therefore, to employ them, is a legitimate object of pursuit, its attainment is within the bounds of possibility, and although it may ultimately fail, the effort may yet reflect great credit on the individual who makes it.

One of the vapour engines for which a patent has been obtained in England, will be found figured and described after that of Brown; we do not deem it necessary to make any particular remarks upon its structure, as our objections are of a general nature, resulting from the unavoidable defects in workmanship, and the necessary consequences of wear, and derangement, incident to all machines, and particularly to those which are massive.

Description of Mr. Brown's engine, in that form of it in which it was intended to raise water, which afterwards flowing upon an overshot water wheel, was to give motion to machinery.

The two cylinders, c and d, are the vessels in which the vacuum is to be obtained; from these descend the pipes gig and hjh, leading into the lower cylinders, which communicate with a reservoir of water, and from which the water rises along those pipes to fill the vacuum cylinders alternately. The water thus supplied is discharged through the pipes B into the tank or trough z, whence it falls upon the overshot water-wheel, and by the rotatory motion thus produced, gives power to such machinery with which it may be connected. The water runs from the wheel, along a case surrounding its lower half, into a reservoir y, from which the lower cylinders xx are alternately supplied,

In order to produce the vacuum, the necessary quantity of gas is supplied to the cylinders by means of the pipe kkk, to be conveniently attached to a gasometer. The gas also passes along the small pipe 11, (communicating likewise with the gasometer), and being lighted at both ends of that pipe, is constantly burning for the purpose of igniting the gas within the cylinders.

The water in the reservoir v, passing down one of the pipes w into one of the lower cylinders x, causes the float y, in that cylinder, to rise, and pushing up the rod o, raises the end b of the beam, which of course draws up with it the cap f, and forces down the cap e of the other cylinder c

The gas being admitted along the pipe k, the flame from the pipe I is now freely communicated to the gas in the cylinder through the orifice, by the opening of the sliding valve s, which is raised by the arm r, lifted by the rod o, by means of the beam.

To produce the intermitting action of each cylinder, some subordinate machinery is put in operation, by chains and rods attached to a glass or iron vessel p, partly filled with mercury, and, turning upon a pivot, each end receives its movements of elevation and depression from the rise and fall of the projecting arms q, by the action of the beam above; the mercury being furnished for the purpose of regulating the supply of the gas into the cylinders, and the movement of the slide in the trough v. By the action thus communicated, the water from the reservoir flows down the pipe w into the vessel x, and produces the elevation of the float y and the rod n, and raises the cap e by the ascent of the beam at a.