We extract from the Edinburgh Philoso phical Journal, the following description of a "self-generating gas lamp," a title which is equally applicable to every other kind of lamp, since all generate the gas from which the light is obtained; the difference is, that in this lamp the oil is decomposed and con verted into gas by failing on a substance previously heated, and the gas is ignited as it issues from the orifice of a tube situated beneath the decomposing chamber, the heat of which is maintained by the flame of the gas ; whereas, in the ordinary lamps, the oil is decomposed and ignited at the same point, viz. at the wick. " The oil vessel of this lamp is represented 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, under neath, is collected ; the dotted lines are projecting ridges on it within the gene rator, to prevent the oil running down and eollecting 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 ; Lis a tube to supply the vacancy in it with gas, as the oil is discharged into C; H is a metal heater to fit into D. To use the lamp, fill A par tially 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 40 drop slowly on the heated bulb D below, by which it will be converted into gas. When it is found to escape 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 effbctually the atmospheric air from and tubes. The principle of this lamp is the same as that of Mr. BI en (from which probably the idea was taken), viz. to decompose the oil by causing it to pass over an incom bustible substance heated to redness; but the arrangements are more complex and not so efficient. Besides the objection to the detached heater, from the trouble of heating so large a mass, in comparison with the incombustible wicks in Mr. Blackadder's plan, the decomposing vessel being of metal, will be found far inferior in effect to glass tubes or similar substances of inferior con ducting power, and in a short time would soon become incapable of decom posing the oil, as it is found necessary at the Oil Gas Works to introduce into the retorts pieces of broken bricks, coke, &c. or plates of iron, which are renewed daily. The decomposing chamber D, 'and the circular rim E, both of which require to be situated over the flame of the lam are also highly objectionable, not only as cumbrous and unsightly appen s, but on account of the dark and extensive shadow which they woul throw upon the ceiling. The size of wick must be proportioned to the degreeof light the lamp is required to afford, but with the ordinary wicks, composed of cotton yarn slightly twisted, if the diameter be much increased, sufficient air does not arrive at the central part of the flame to cause the entire combustion of the fuel, and the lamp consequently burns with much smoke, and a depbait of carbonaceous matter upon the wick takes place; it is therefore found preferable to use two or more small wicks instead of one larger one. Count Rumford, whose experiments upon warming and lighting have produced such great improvements in these two branches of domestic eco nomy, invented a lamp, the wick of which is formed of a kind of broad tape wove for the purpose ; and, as a reading lamp, it is equal to any, whilst at the same time its construction is extremely simple : but the greatest improvement yet made in lamps, is the Argand lamp, so named from their inventor, M. Argand, of Geneva. The distinguishing feature of these lamps is that the wick is hollow or tubular, and the wick-holder is so constructed as to allow a passage for the air through the centre of the flame, as well as on the exterior, by which means every particle of the oil is decomposed and burned, and a most brilliant flame is produced, free from smoke or smell. When oil of the best quality is used, lamps of this description are found infinitely superior to all others for all situations where they do not require to be moved about, and are now manu factured in an endless variety of the most tasteful and elegant forms, and with various additional contrivances for regulating the height of the flame, the flow of oil, doing away with shadow of the oil vessel, &c. The annexed cut repre sents a very common and simple descrip tion of Argand lamp, adapted either to stand upon a bracket, or hang against a wall. In these lamps the oil surrounding the wick is maintained constantly at the same level, by a contrivance similar in principle to the bird fountain. a is the oil reservoir or fountain, closed at the top, but having an aperture at bottom fitted with a conical or button valve. The reservoir fits loosely into an outer case 6, so as to allow free admission for the air between the two ; c is the neck by which the oil flows into the wick-bolder d, which is composed of two concentric tubes joined together at the bottom by a circular plate, having an aperture in its centre for the passage of the air to the centre of the flame, equal to the aperture of the interior tube ; a is the circular wick, fixed upon a ring, which can be raised or lowered at pleasure, by a contrivance which will require a separate diagram for its illustration. f is a glass chimney, to cause a more rapid current of air, and g is a ground glass shade, to equalize the light and soften the glare. To charge the lamp, the vessel a is withdrawn from the casing b, and, being inverted, the valve falls inwards, leaving the aperture open by which the oil is to be intro duced. When the reservoir is filled, the aperture is closed by pulling up the wire, or tail, projecting from the valve, and the reservoir may be returned to its erect position without any escape of oil. Upon replacing it within the casing b, before it quite reaches the shoulder of the case by which it is supported, the tail of the valve rests upon the bottom of the cue, and the valve is pushed inwards, upon which the oil flows from the reservoir into the casing and wick holder, until it touches the bottom of the reservoir, which descends a little below the level of the wick-holder, when the admission :of the air into the reservoir being prevented by the oil in the casing b, covering the aperture, no more oil can escape. Upon lighting the lamp, as the oil rises to the wick by its capillary attraction, the level falls in the casing b, and the aperture in the vessel a becoming uncovered, the air enters and expels a fresh portion of oil, until the level of the oil rises in the case and closes the aperture ; and thus, during the time the lamp continues lighted, the oil in the casing and wick-holder is constantly maintained at the same level : a small cup Is is screwed on below the wick holder to receive any oil which may chance to overflow ; care being taken that the cup shall be so far below the circular aperture of the wick-holder as not to impede the passage of the air to the flame. We shall now proceed to describe the means by which the wick is raised or lowered in order to regulate the flame. The adjoining figure represents a sec tion of the wick-holder, except that part of the internal tube is shown entire in order to ex hibit more clearly a spiral groove which makes two or three turns round it. a is the wick, the lower end of which is drawn over a small metal ring b, which has a small stud c, projecting each way, the internal end entering the spiral groove on the surface of the centre tube, and the external end passing through a longitudinal slit or groove, extending the whole length of a tube d, which is soldered into a ring, or collar, resting upon the to of the external tube of the wick-holder; from this ring, or collar, proceed the bent wires e e, which sup port the rim f, upon which the chimney rests. Now, upon considering the figure, it will be seen that on turning the rim f, the tube d, which is connected with it by the bent wires e e, will also be turned round, and will carry with it the ring b, by its stud c; and as one end of the stud is engaged in the spiral groove, it will, in turning round, either ascend or descend along the groove, according to the i direction in which it is turned : Is is the tube by which the oil flows to the wick, and k is the cup to receive any overflowing'. When lamps are required to give light in one direction, as when placed against a wall, or used as reading lamps, the fountain lamps, similar to that just described, are undoubtedly superior to all others, on account of the abundant and uniform supply of oil which they afford to the wick ; but when a lamp is required to throw a light all round, as when placed on a table in the centre of a room, the fountain becomes objectionable on account of the shade it throws; in this case the burner is usually mounted upon a column, and is encircled by a hollow ring at a distance of some inches from it, containing the oil which flows to the burner by two tubes, and in order that the level of the oil may not greatly vary, the ring is made as flat as This ring also supports a ground glass shade, which. besides softening by its peculiar form, so reflects and refracts the rays in every direction as nearly to prevent any shadow being casthy the reservoir; hence these lamps are termed smumbra," or " shadowless lamps." But although the shadow thrown by such lamps is scarcely perceptible, the light is not equal to that of fountain lamps, owing to the supply of oil being neither so copious nor so uniform as in the latter; and they are also somewhat cumbrous and awkward to move, owing to the projection of the reservoir and glass shade, and to the centre of gravity of the lamp being carried so high up. To remedy these defects has long been a favourite specu a with many persons, and generally every year one or more patents are taken out for lamps which are supplied with oil from a reservoir situated within the column which supports the burner. Few of these possess any claims
to novelty, kilng most of them founded upon the principle of the Chremnitz fountain, in which a body of water descending through a given height forces a smaller quantity of water, contained in a close vessel,up to nearly an equal height by compressing the air above its surface. As illustrative of the prin ciple we shall describe one or two of these lamps, although as we have already remarked, few of ,them exhibit much originality of thought. The figure on page 36 represents an arrangement for a lamp described in the Register of Arts as the invention of a correspondent in which the resemblance to the Chremnits fountain will be at once recognised. a is a vessel containing water ; b an oil vessel; c c a column and pedestal to support the lamp, closed at the top and bottom, and forming the air vessel ; an air tube in a, open at top and bottom; e a tube soldered into the top of the column c, and proceeding from the bottom of a to the bottom of cup f; g a similar tube soldered to c, and proceeding from b, the lower end descends a little way into the cup h; i is a glass tube ascending from the bottom of the cup h, through a tight joint, and branching at top into three capillary jets, forming the burner, and the tube 1, which surrounds it, serves to receive any oil that may flow over; in and a are two plugs in the bottom of e and g. T. use the lamp proceed as follows : —Invert the lamp, withdraw the plugs in and is, fill a with water, and b with oil; then replace the plugs in the position shown in the drawing, and place the lamp on its base. The oil will now flow from b into h, until the month of the tube g is covered; at the same time the water flowing from a into f will compress the air in c, which, acting on the surface of the oil in h, will force it up the tube i to the burners ; by this the oil in h will fall below the mouth of g, when a portion of the compressed air passes into b, displacing an equal bulk of oil; by these means the oil in k is always maintained at the same level as the mouth of g ; the capacity of a is not equal to that of the base up to the level of the brim of the cup but it is clear that by means of the air-tube d, the height of the column of water will always be equal to the height of the lower opening of d, above the brim of f. To extinguish the lamp, push the plugs in and a into the necks of e and g, which stops the supply of oil. The cup f is screwed into the bottom of c, and must be unscrewed to discharge the water in c, when the vessel becomes empty.
In the ;ketch on page 38, Fig. 1, represents a section of a lamp invented by Mr. Bright, of Bruton Street, which was exhibited at the National Repository, and which we have seen in use elsewhere, and it appeared to us to afford a strong and steady light. The principle is precisely similar to that of the one just described, but it is much more compact, and the general arrangement is better. This lamp, and the mode of its action, may be briefly described as follows :—The water vessel b is an inverted fountain, which empties itself into the air chamber a, through the pipe d; the air thus displaced is forced up the rising bent tube e into the oil vessel a, from whence, as it cannot escape, it presses upon the oil and forces it up the pipe f to the burner g. It will be seen that by this arrangement the two columns of oil and water will be constantly in equilibrio.
The last lamp upon this static principle which we shall notice, differs somewhat from the preceding, and s rather more novelty. It is represented in sec tion on p. 38, Fig. 2, is an extract from the inventor's description of it in the Register of Arts a glass vessel forming the body of the lamp ; surmounted by a glass column connected with a by the cork c, which fits tightly into each, and closed at top by the cork h. No. 2 a glass tube descending through the two corks h and c, to the bottom of the vessel a, and bent upwards far as;, it communicates with the column by the hole f, which may be by a sliding tube 5, and the latter be closed by the stopper k at its top. No. 1 a glass tube passing through the corks h and c, its lower end opening into a, and its upper connected by a stop cock with d, a glass weed closed at top and bottom with corks. e a capillary tube descending half way down d No. 3 a tube passing through h and c, and reaching to the bottom of a; it has two Mall openings into the column in its upper part, which may be closed by the stopper L No. 4, (not seen in the section, but shown in Fig. 3, which is a plan of the tubes,) is a tube passing through h and c into the upper part of a. The mode of filling the lamp is as follows : close the hole/ in No. 2, and open l, 2, and 3, and through 5 pour quicksilver till a is filled to the level of the top of the bent leg g, then close 5 by its stopper k. In the top of 3 insert a bent tube, (shown by the dotted lines,) and suck the air out of the column, when the mercury will rise in 3, pass through the holes in its upper end, and occupy the space shown by the dotted lines. Remove the bent tube, and insert the stopper 1, and through 4 pour water into a, up to the line b b, and oil up to the cock c, and close No. 4, and the operation is complete. When the lamp is wanted for use, take the stopper out of No. 5, and raise 5 tiU the hole f becomes open, when the mercury will descend and pass over g into the bottom of a, forcing the oil up No. 1 to the burner e, to which a light being applied, it will continue burning steadily till the oil in a and the mercury m i are ex hausted, when the lamp is to be refilled by exhausting the air in i, and pouring oil through No. 4. The flame may be regulated or extinguished by means of the stop-cock. The height of e above g may be equal to, but must not exceed, that of a column of oil, whose pressure shall be equivalent to the pressure of the column of mercury.
From the foregoing description, it will be seen that the columns of oil and of mercury always maintain their respective heights, and the supply of oil to the burner is consequently always uniform. The inventor states, that the lamp (which was merely got up for an experiment) afforded a steady light upon trial.
In the lamp which is represented in section in the annexed engraving, and which is the invention of R. F. Jenour, the air is compressed in a closed reservoir, by means of a condensing syringe, and a communication being formed between the air chamber and the oil chamber, the air by its expan sion forces the oil up the supply pipe to the burner. The body of the lamp is divided into three compart ments by two discs, a and b; c is the oil vessel, d a space to receive the overfiowings from the burner, and e the air vessel ; f is a condensing syringe, the piston rod of which g is hollow ; the lower end of the syringe is closed by a valve h, pressed against it by springs; a rod from this valve passes through g, and can be screwed up by the nut k; 1 is a tube connect ing the oil vessel c with the air vessel e, which has another aperture to the atmosphere, closed by the nut m; n is the tube for supplying the burner, having a capillary tube o, cemented into its lower end, which descends to the bottom of the oil vessel ; p is a stop-cock for cutting off the commu nication with the burner, which being of the common description is not shown. The middle compartment d opens to the atmosphere by a short tube q, surrounding n; r is a tube opening into c ; it is pierced with numerous holes at the lower end, and is closed by a valve which is secured by a nut s screwing on to the top of a rod attached to the valve ; t an air pipe descending from the to of e to the bottom of c ; the air, therefore, ascends through the oil in c, and collects above its surface and in the air vessel d. To charge the lamp with oil unscrew the nut es, and slacken the nut f, then pour in oil by the tube q, and it will descend into c through the holes in r; the nuts m and s must then be screwed down again. The nut k must now be unscrewed from the rod of the valve h, and the air injected by the syringe, taking care to close the orifice of the piston rod, by applying the finger to it at each stroke ; when the resistance against the valve increases, till the syringe can no longer be worked, the nut k must be again screwed on, and the lamp is ready for use, by merely opening the stop-cock p. There have been many lamps upon the principle of the one just described, but from the difficulty of regulating them, they have not come into general use ; this difficulty arises in part from the continually varying pressure of the condensed air, occasioned by its increase of volume as the oil consumes, and also from the difficulty of regulating the supply of oil to the burner, so as neither to overflow nor fall short of what is required. In a lamp invented by Mr. Machell, a dew of cotton is introduced through the bore of a cock, when, by turning the p the passage may be regulated with considerable accuracy. In the present ..p, the patentee effects this by a capillary tube, which retards the flow of oil in proportion as it is lengthened, and this is the principal improvement claimed in the patent. The objection to this seems to be that the flow cannot be regulated at pleasure. Upon the whole, although many of the lamps with the oil reser voir contained in the base, exhibit considerable ingenuity in various parts of their details, yet very few have been found to answer in practice, being mostly either troublesome to manage, or unequal in their action ; and the only lamp of this description which we have yet seen which seems to be of decided prac tical utility is one of French invention. In this lamp there are two small pumps worked by a train of clock-work situated beneath the reservoir of oil in the pedestal of the lamp. These pumps, which in their construction resemble a'pair of bellows, work with very little friction, and impel the oil in a copious stream to the burner, and no inconvenience can result from an excess in the supply as the overflow merely returns into the reservoir.