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The holes heing of the same dimensions in each 1 urner. Various statements have been given of the illuminating power of oil and coal-gas; nor is this to be wondered at, when we considerthat the quality of the gases depends so much on the mode of preparation, and take into account also the defective modes usually adopted for determining the intensity of the light afforded by their combustion. Mr. #. in his early papers on this subject, has given a very flattering account of oil gas. He states, that an Argand burner, giving a light equal to six candles, six to a pound, consumed one cubic foot per hour; and, as Mr. Accum mentions, that an d of coal-gas, giving a light equal to three candles, eight to the o: consumes two feet in the same time, he has inferred, supposing the candles of the same size, the illuminating power as 4 to 1; but, taking the average of a number of experiments, he has fixed their comparative power of giving light as 34 to 1. In these trials, however, the gases were not brought into comparison with each other by burning them together, and the data on which he proceeds seem to be very fallacious, as it is not stated whether the candles were of the same kind in both experiments. Messrs. Taylor and Martineau have, however, come to nearly the same conclusion, that the illuminating power is as 34 to 1, a conclusion drawn from the experiments of Mr. Brande and Mr. Faraday. A gentleman connected with the Liverpool Gas Company, in the answers to the queries put to him by the committee of the Dundee Company, replies, that the relative quantity of gas requisite to supply the same light, is as 14 oil-gas to 51 coal-gas, making their power of affording light rather more than 3} to 1. Though the above statements place the illuminating power of oil-gas so high, a very different account is given by others. According to Mr. Neilson, Glasgow, it is not to be rated at above 2, or at all events beyond 24, to the other as 1; and the same conclusion is drawn from a series of experiments made at Bristol, by Messrs. Herapath and Rootsey, on whose results, Mr. Peckstone has remarked, that every reliance may be placed, as they could not be actuated by party-feeling, but solely by a desire to ascertain the truth. These statements, so very discordant, must arise either from the defective mode of ascertaining the intensity of the light, or from the variable quality of the gas, both of which have had their effect. The mode usually followed for ascertaining the illuminating power, viz. of producing the

same intensity of shadow, and marking the quantity of the gas consumed in a given time is liable to many objections. It is extremely difficult, for instance, to judge with precision of the depth of shadows; besides, unless each gas is burned under circumstances favorable for producing the greatest light, the conclusion with respect to their power of illumination is not correct. Some of the experiments in which the oilgas is stated as 3} to 1, it has beer said, were conducted by using burners of equal dimensions for both : now, it is well known that the former requires a smaller one than the latter, otherwise the intensity of the light is not in proportion to the gas consumed, part of it probably escaping combustion. The remark, with respect to the variable quality of the gas, is also of equal force. In a paper published by Mr. Dewey, in the Annals of Philosophy, some experiments on the illuminating power of the gases are stated, with a view of “setting the matter at rest.’ This we conceive they have done, as far as can be ex}. ; but we suspect the conclusion to be drawn m them, is very different from that at which Mr. Dewey arrives. The gases were taken from main-pipes running parallel to each other, the coal-gas from the Imperial Gas Works, the other from that at Bow. Being burned so as to afford the same intensity of light, the quantities were found by accurate metres to be (taking the mean of seven trials) as 4850 to 1368, very nearly 3} to 1. It has been supposed by some, that the specific gravity of coal-gas is a good test of its purity, the lighter it is, the greater being its ower of illumination. The experiments of Dr. Henry, and others, however, disprove this; indeed, after the gases are properly purified, the heavier they are, so much the more will be the light afforded by their combustion. The gas used by Mr. Dewey was of specific gravity .406, now this was less than pure carbureted hydrogen, which is 555. In a note to the same paper, the editor remarks, that the results .P ki. Dewey coincide with those obtained by him and Mr. Faraday. The coal-gas they subjected to trial was, in one instance, of specific gravity ‘429, in another, 406. The oil-gas was 965 and '939, and their illuminating power to the former was as 3} to 1. As the coal-gas in all of these experiments was of inferior specific gravity to carbureted hydrogen, we may reasonably infer, that they contained a considerable proportion of pure hydrogen, which, it is well known, affords a very feeble light. Dr. Henry has found the gas to vary in specific gravity from 345 to 650, its illuminating power increasing as it approached the maximum. The specific gravity of the coal-gas of Edinburgh, which is allowed by all to be of very superior quality, has been found to be so high as '680. The oil-gas used by Mr. Dewey was 939. Dr. Henry mentions, that in some of his experiments it was 906. Dr. Fyfe found that from the small apparatus of Mr. Milne (Taylor and Martineau's), to be 940, and which is generally allowed to be very fine, so that we take it for granted, that that of Mr. Dewey was of good quality. If then, in these trials, a good oil-gas, pitched against a very inferior coal-gas, is only as 3} to 1, the illuminat

ing power of the former must be much reduced when brought in competition with the latter when of equally good quality; consequently, it must be far short of that stated by Mr. Dewey. Dr. Henry, in his paper on the nature of the gases produced by the decomposition of coal and oil, proposes to ascertain i. illuminating power by finding the quantity of oxygen necesssry for their combustion; for, according to him, the more a gas will consume, the more light it will afford. He has found, that oil and coal gas, produced under different circumstances, take different quantities of oxygen.

Specific gravity. Oxygen. 100 volumes of coal-gas of 345 took of 78 Ditto . . . . 500 — 166 Ditto . 620 — 194 Ditto . . . . 630 — 196 Ditto . . . 650 — 217 100 volumes of oil-gas of 464 — 116 Ditto , 590 — 178 Ditto 758 – 220 Ditto 906 — 260

From the above tables it would, of course, be inferred, that the illuminating power of oil-gas, No. 4, is the greatest; that of coal-gas, No. 1, the least, these being to each other as 260 to 78; that is, as 34 to 1. From this, then, it appears, that the best oil-gas is to the worst coal-gas as 34 to 1; of course a very different conclusion with respect to their illuminating power would be drawn, were we to take an average from the above tables, by which we should diminish the light given out by the former, and increase that from the latter.

The gaseous matter, given off from coal and oil, now known by the name of coal and oil gas, contains nearly the same ingredients, but in different proportions. Dr. Henry has shown, that they are mixtures of hydrogen, carbonic oxide, carbureted hydrogen, and olefiant gas, with occasionally a little nitrogen; and, in addition to these, coal-gas, before it is subjected to the process of purification, always contains ammonia, carbonic acid, and sulphureted hydrogen; but from which it is, or at least ought to be, freed before it is sent into the gas-holder; so that both gases, when exposed for sale, contain the same ingredients, but in different proportions. There is also given off, during the decomposition of coal and oil, an essential oil, which seems to be held in solution, in a state of vapor, in the gas, and which is the cause of the smell, and, as some suppose, adds to the illuminating power.

Dr. Henry, in his paper in the Annals of Philosophy for September 1821, has given the component parts of different samples of gas. The coal-gas was prepared from Wigan Canal, at the manufactory of Messrs. Phillips and Lee, and collected from an opening in a pipe between the retort and the tar-pit, generally about half an hour after the commencement of the distillation, except in the instance of the gas No. 4, which was taken five hours, and, No. 5, ten hours from that period; the carbonic acid and sulphureted hydrogen being removed by washing it with solution of potassa.

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The gas condensed by chlorine is supposed to be partly olefiant, and partly a volatile oil. That not condensed, the above tables show to vary in its composition. In the best specimen of oil-gas, the carbonic oxide is in larger proportion than in the best kinds of coal-gas; and the carbureted hydrogen is most abundant in the latter. The hydrogen in both appears to increase as the temerature at which they are formed becomes o and is always greatest in the last proportions. It has been proposed in Holland to substitute turf for coal, or oil, as a material from which to obtain a gas for illumination. The experiments that have been made promise much success; and the apparatus required may be of far simpler construction than those used in the distillation of coal. The products do not require that careful and elaborate process of purification which is necessary for the gas from coal. It is said also that the light is better. The light may be better than that from coal-gas badly made, or carelessly used; but it is not likely that, with equal precautions, the first should surpass, or even equal the latter. With reference to the arrangement of the pipes, by which gas is distributed for the purpose of illuminating cities, it may be proper to state that all gas mains laid in public streets should be placed at least eighteen inches below the surface of the ground, to secure them from being disturbed by carriages, or interfering with the paving of the street; they should be placed o firm, so that they may not easily give way. The course of the pipes should be rectilinear, with a dip of about one inch in every ten feet distance. In all wide streets, where the number of houses on both sides of the streets, to be supplied with gas, is numerous, it is more economical to employ a separate gas main for each side of the street, than to make use of one larger main for both sides; because smaller mains may then be employed, and the collateral branch pipes leading into the houses are shorter; these circumstances amply compensate for the additional main. All branch pipes proceeding from a main should have a dip of about one inch in ten feet, towards the main from which they proceed, so that any fluid that may happen to collect in these pipes must run into the mains. All small wrought-iron branch pipes proceeding from the mains into the houses, or places to be lighted with gas, should be covered with a thick coat of coal tar, before they are laid down into the ground; this may easily be done by heating the pipe, and laying on the boiled tar with a brush. Every separate length of branch pipe should be tried by condensing the gas in the pipe under water, in order to be certain that it is sound. The junctures of these pipes should be made by dipping the male screw of the pipe into a mixture of white lead and linseed oil, before they are screwed together. Notwithstanding the usual care which can be taken in proving pipes, before the gas is admitted into them, a slight leakage may be sometimes subsequently detected. Therefore, before the gas is suffered to enter the mains, they should be again proved, in order to be certain that all the junctures are air-tight. The most convenient manner of proving the mains when laid, is by means of a small portable gas-holder filled with common air, and connected, by means of a small pipe, with the system of the mains, to be tried. is gas-holder should be made to act with a pressure at least four times greater than the pressure which the pipes will have to sustain by the gas they are to convey. If the mains are air-tight, the gas-holder will remain stationary; but, if they are not sound, the gas-holder will descend in proportion to the leak of the mains; the quantity of gas lost may be thus ascertained. . In order to guard against the danger of water entering from the external surface into the pipes,

a reservoir should always be placed at the lowest point, where two or more descending mains meet and form an angle, so as to receive the water that may happen to collect at this angular point, an accumulation of which would cut off the communication between the two pipes: this reservoir is usually called a syphon. It ought to be at least twice the diameter of the bore of the mains, between which it is interposed, and four times that diameter in depth. These reservoirs afford the best indication to show the sound or leaky state of the system of the mains. In all instances, where the pipes are perfectly sound, observation has shown, that half a mile of gas-mains, three inches in the bore, does not deposit more than a quart of water in a year; on the other hand, if the mains are leaky, the water of the reservoir requires to be pumped out, sometimes as frequently as every fortnight; and, during wet weather, much oftener. The loss of gas by such leakage is much greater than is generally imagined. Instances might be mentioned where, in order to keep the common air out of a system of faulty pipes, a constant influx of gas, which a pipe two inches in diameter can supply, has been found necessary and this, of course, is just so much gas lost to the economy of the establishment. With regard to the diameter of the mains, no general rule can be given. It must vary according to the number of branch-pipes and lamps which the main has to supply within a given distance,—the angular direction of the mains,—the pressure of the gas-holder, and, above all, with the relative altitude of the place where the gas-holder is situated, and the place at which the gas is to be supplied, or where the lamps are placed. Indeed, this is one of the most important considerations with regard to the economical distribution of gas-mains; and, by attending to this circumstance, a prodigious saving may be effected. In order that the pipes for conveying the gas from the mains, and distributing it through the houses or other buildings to be lighted with gas, may, in the first place, not be unnecessarily large, or too small, the following rule may serve as a guide to workmen:— One gas-lamp, consuming four cubic feet of gas in an hour, if situated twenty feet distance from the main which supplies the gas, requires a tube not less than a quarter of an inch in the bore. Two lamps, thirty feet distance from the main, require a tube three-eighths of an inch in the bore. Three lamps, thirty feet distance from the main, require a tube three-eighths of an inch in the bore. Four lamps, forty feet distance from the main, require a tube half an inch in the bore. Six lamps, fifty feet distance from the main, require a tube five-eighths of an inch in the bore. Ten lamps, 100 feet distance from the main, require a tube three-quarters of an inch in the bore. Fifteen lamps, 130 feet distance from the main, require a tube one inch in the bore.

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Mr. Phipson, of Birmingham, in order to obviate the effects produced by the action of gases on copper or brass pipes, through which th , has adopted the plan of lining them . o A tube is formed of rolled copper, by drawing it through a plate, and the edges are soldered together, so as to form a safe joint, the superfluous solder is dressed off, and the tube again drawn; a piece of lead-pipe is then drawn through a plate on a mandrill, of the diameter of the tube required, and placed within the copper pipe; then, by passing through it a conical mandrill attached to a rod, the lead-pipe is forced against the inner surface of the copper tube, so as to leave them in perfect contact; or, sometimes a lead-pipe is prepared on a mandrill, of the diameter of the tube required, and a copper-pipe, already soldered, drawn over it; they are then passed both together on a mandrill through a draw-plate, so as to bring the two into complete contact. The lead-pipe is proof against the action of gas, and the copper-pipe, at the same time that it supports and defends it, makes a better appearance.

Four gasometers of 25,000 feet each have been erected on a new principle at Ashton-underLyne Gas-Works, and in practice it is found to answer very well; there are four iron pillars at the four points of each gasometer, with an endless chain fixed and made tight round the pillars and gasometer; the latter is attached on one side of the pillars only, by which means it rises and falls as other gasometers. On this principle they are not acted on by the wind, though exposed; and another great advantage is, they are much cheaper than those erected on the old principle.

The great improvements which have taken place, both in the manufacture of gas, and in the methods of applying it for the purposes of illumination, render it extremely probable that it will be much more extensively employed in lighting up private houses. Many persons object to introduce the gas directly into their apartments; and it has accordingly been proposed to bring the gas to the windows, to allow it to burn on the outside, and thus to illuminate the room without any of the annoyances which arise, both

from the smell of the gas, and from the heat generated during its combustion. In order to do this to the greatest advantage, the gas-pipe should be brought to the cill of the window, and should then have a gas-tight joint by means of which it can be placed either vertically, when it is to be used, or horizontally, when the apparatus is to be removed altogether, or put aside during the day in a press or recess made in the wall to receive it. 1. lamp which is to protect the gas from wind and rain, should have fronts of glass either hemispherical or semicylindrical, so that no opaque line or bar may interfere with or break the cone of rays which enters the window. The back part of the lamp must be a reflector, of such a surface that it will throw into the apartment all the rays that would other

wise not enter. The direct and reflected light

which thus enter apartments, might be rendered uniform, by means of an ornamental blind of the finest muslin (varnished or not as may be found most advantageous); and, if the blind has a landscape upon it, the most luminous portion, or that nearest the gas flame, might be made to have the appearance of the sun in the heavens. In newly built houses, recesses might be constructed, in such a way that the lamp and gastube might turn round a joint, and be entirely concealed from view in the day-time. The advantages of such a method of illumination are great and obvious. Instead of being annoyed by the constant entrance of servants to trim the lamp;-instead of having the furniture destroyed by the spilling of oil, and by the carbonaceous matter necessarily produced either by oil or wax burning within an apartment;-instead of having the temperature of over-heated rooms increased by the heat of the lights;–instead of having the eye injured by the irritation which arises from brilliant flame;—and instead of having the apartment illuminated by a light constantly varying in intensity, wa shall avoid all these evils, and have our houses lighted in the very same manner as they are by the light of day. The disadvantages which attend this method are very few. They are prevented from excluding the cold air of winter by shutters and curtains; but in many cases this is an advantage, and, when it is not desirable, the heat on the outside of each window will diminish the currents of cold air which might otherwise be admitted. A greater j.". of light will no doubt be necessary to prouce the same degree of illumination; but the cheapness of gas renders such an objection of no weight. The application of inflammable gas to the purposes of illumination, has hitherto been almost wholly confined to the lighting of large cities, extensive manufactories, and public institutions. The ingenious apparatus invented by J. and P. Taylor, for obtaining gas from oil, has enabled gentlemen of fortune to light their houses with gas at a moderate expense, and without being annoyed by any of the disagreeable products which arise from the distillation of coal. But, notwithstanding this valuable improvement, gas-light has never been rendered generally portable, and the great body of private individuals, and all the lower classes of society, are unable to

derive any advantage from the extraordinary cheapness of this beautiful light. In order to remove these limitations to the use of gas lights, and to render them available in nearly every case where lamps or candles can be used, Mr. Gordon conceived the idea of condensing a great quantity of gas into a small space, and set himself to construct a lamp in which this condensed gas could be burned with the same facility and security as an ordinary lamp. The body or reservoir of the lamp is commonly made of copper, about one-twentieth of an inch thick, in the form of a sphere or a cylinder with hemispherical ends. This reservoir may be put into a different apartment from that which is to be illuminated, or may be concealed under the table, or, when it is required to be ornamental, it may be put into a statue, or the pedestal of a statue, or may be suspended. n order to regulate the escape of the condensed gas, Mr. Gordon has employed two different contrivances, which are extremely ingenious. The first of these is a stop-cock, constructed in the following manner:—After the cock has been drilled through, in the usual manner, the circular hole in the key is contracted at one side, by soldering into it two pieces of brass, which join at one side of the hole, and are about one-twentieth of an inch distant at the other side, forming an acute angular aperture. By this means the issue of gas can be regulated to the smallest possible stream, by bringing the acute angle of the opening in the key to communicate with the circular opening in the cock; and, as the expansibility diminishes as the gas is consumed, the aperture can be increased in the same proportion. But to secure the above object more completely, and to prevent the possibility of turning the cock suddenly, so as to admit too great a discharge of gas, a ratchet wheel is fixed in the end of the key of the cock, in which an endless screw works. By turning this screw with the nut, the flame may be enlarged or diminished to any extent, however highly condensed the gas may be. The second contrivance which Mr. Gordon employs to produce the same effect, is a conical leather-valve, similar to that in the reservoir of an air-gun, placed in the opening of the reservoir of the lamp, where it screws on to the condensing pump. When the reservoir has been charged with gas, and removed from the pump, a brass instrument is screwed in above the valve. Through this piece of brass there passes a fingerscrew, the point of which, when made to press on the valve, forces it back, and allows the gas to issue in any quantity that may be required. A bridge of brass, consisting of a hollow tube, in the form of a Gothic arch, passes over the head of this regulating screw, for the purpose of giving freedom to the fingers in turning the screw to regulate the flame, and to conduct the gas to the burner, which, in a standing lamp, is screwed on at the centre of the arch. - By either of these contrivances, the latter of which Mr. Gordon prefers from the simplicity of its construction, the command of the flame is so complete, that it may be reduced to an almost *... quantity. forcing-pump by which Mr. Gordon con

denses the gas is nearly the same as that of the common condensing syringe, having a solid piston worked by a lever, with shears and a guide to produce a vertical motion. As a considerable degree of heat is created during the condensation of the gas, the pump must be kept cool by surrounding it with a case filled with water, and changing the water as soon as it becomes heated. When it is required to fill a great number of lamps with condensed gas, Mr. Gordon employs the steam engine to work the forcing pump, and the gas should be condensed into a large reservoir, from which the lamps of numerous individuals may be filled at once with the condensed gas. A mercurial gauge, similar to that used for ascertaining the force of condensed air, must be fixed to the large reservoir, for the purpose of enabling any person to see the degree of condensation to which the gas has been brought. Although, at the first erection of gas works, the public feeling was strongly against them, on account of their supposed danger and offensive nature, this prejudice has gradually worn off. Though the danger of having large collections of gas has been rated at an enormous extent by Sir William Congreve, only one instance of the explosion of a gas-holder has happened; and this occurred in the first filling of one at Manchester, through ignorance, and the carelessness of the workmen. The atmospheric air, not having been extracted, was of course allowed to mix with the coal-gas; and one of the men, wishing to ascertain if the gas-holder was tight, . a candle to a part, from which gas, mixed with atmospheric air, was issuing, which caused it to explode, and tear the gas-holder in pieces. A few accidents have occurred, from the escape of gas from the pipes, but these have, in general, been oit the carelessness of the workmen, and were of a trifling nature; for when the gas does escape, it is only when it gets into some confined place, as a vault, or a common sewer, that it can, on the approach of flame, do any mischief. Shops and apartments of a dwelling house are not close enough to keep the gas confined; but allowing them to be so, the quantity emitted is too trifling, compared to that of the air. Coal gas is most explosive when mixed with about five of air. In a room, then, of twelve feet each way, one burner, consuming five cubic feet per hour, would be sufficient to light it, but, in this apartment, there are 1728 feet, so that, to get an explosive mixture, and allowing there is no loss of gas, the burner must be left open upwards of fifty hours, or at least two days and nights, which is not likely to happen. When imore lights are used, the apartments are of course larger, so that the same time would still be required. In those cases, also, in which the burners are left open, the odor of the gas gives warning of its escape; so that one of its properties, considered offensive, actually proves a valuable safe-guard. GASCOIGNE (George), an English poet of some fame in the reign of queen Elizabeth. He was born in Essex, of an ancient family, and educated at Oxford and Cambridge. Thence he removed to Gray's Inn, but, having a genius too volatile for the law, he travelled, and for some

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