II. APPLICATION OF LIGHT-GAS._A Dictionary of Arts, Manufactures and Mines containing a clear exposition of their principles and practice

1. _Distribution of the pipes_.--The pressure by which the motion of the

gas is maintained in the pipes, corresponds to a certain height of water

in the cistern of the gasometer. From the magnitude of this pressure,

and the quantity of gas which in a given time, as an hour, must be

transmitted through a certain length of pipes, depends the width or the

diameter that they should have, in order that the motion may not be

retarded by the friction which the gas, like all other fluids,

experiences in tubes, and thereby the gas might be prevented from

issuing with the velocity required for the jets of flame. The velocity

of the gas in the main pipe increases in the ratio of the square root of

the pressing column of water upon the gasometer, and therefore by

increasing this pressure, the gas may be forced more rapidly along the

remoter and smaller ramifications of the pipes. Thus it happens,

however, that the gas will be discharged from the orifices near the

gasometer, with superfluous velocity. It is therefore advisable to lay

the pipes in such a manner, that in every point of their length, the

velocity of discharge may be nearly equal. This may be nearly effected

as follows;--

From experiment it appears that the magnitude of the friction, or the

resistance which the air suffers in moving along the pipes, under a like

primary pressure, that is for equal initial velocity, varies with the

square root of the length. The volume of gas discharged from the end of

a pipe, is directly proportional to the square of its diameter, and

inversely as the square root of its length; or, calling the length L,

the diameter D, the cubic feet of gas discharged in an hour _k_; then

_k_ = D²/√L. Experience likewise shows, that for a pipe 250 feet long,

which transmits in an hour 200 cubic feet of gas, one inch is a

sufficient diameter.

Consequently,

1 D² √(_k_ √L)

200 : _k_ ∷ -------- : --; and D = ---------

144 √250 √L 455,000

From this formula the following table of proportions is calculated.

+---------------+---------------+----------+

|Number of cubic|Length of pipe,|Diameter, |

|feet per hour. | in feet. |in inches.|

+---------------+---------------+----------+

| 50 | 100 | 0·40 |

| 250 | 200 | 1·00 |

| 500 | 600 | 1·97 |

| 700 | 1000 | 2·65 |

| 1000 | 1000 | 3·16 |

| 1500 | 1000 | 3·87 |

| 2000 | 1000 | 4·47 |

| 2000 | 2000 | 5·32 |

| 2000 | 4000 | 6·33 |

| 2000 | 6000 | 7·00 |

| 6000 | 1000 | 7·75 |

| 6000 | 2000 | 9·21 |

| 8000 | 1000 | 8·95 |

| 8000 | 2000 | 16·65 |

+---------------+---------------+----------+

These dimensions are applicable to the case where the body of gas is

transmitted through pipes without being let off in its way by burners,

that is, to the mains which conduct the gas to the places where it is to

be used. If the main sends off branches for burners, then for the same

length the diameter may be reduced, or for like diameter the length may

be greater. For example, if a pipe of 5·32 inches, which transmits 2000

cubic feet through a length of 2000 feet, gives off, in this space, 1000

cubic feet of gas; then the remainder of the pipe, having the same

diameter, can continue to transmit the gas through a length of 2450 feet

= (450,000/_k_)², with undiminished pressure for the purposes of

lighting. Inversely, the diameter should be progressively reduced in

proportion to the number of jets sent off in the length of the pipe.

Suppose for instance, the gasometer to discharge 2000 cubic feet per

hour, and the last point of the jets to be at a distance of 4000 feet.

Suppose also that from the gasometer to the first point of lighting, the

gas proceeds through 1000 feet of close pipe, the diameter of the pipe

will be here 4·47 inches; in the second 1000 feet of length, suppose the

pipe to give off, at equal distances, 1000 cubic feet of gas, the

diameter in this length (calculated at 1500 cubic feet for 1000 feet

long) = 3·87 inches; in the third extent of 1000 feet, 600 cubic feet of

gas will be given off, and the diameter (reckoning 700 cubic feet for

1000 feet long) will be 2·65 inches; in the fourth and last space (for

200 cubic feet in 1000 feet long) the pipe has a diameter of only an

inch and a half, for which, in practice, a two-inch cast iron pipe is

substituted; this being the smallest used in mains, into which branch

pipes can be conveniently inserted.

The same relations hold with regard to branch pipes through which the

gas is transmitted into buildings and other places to be illuminated. If

such pipes make frequent angular turnings, whereby they retard the

motion of the gas, they must be a third or a half larger in diameter.

The smallest tubes of distribution are never less than one fourth of an

inch in the bore.

Where, from one central gas work, a very great quantity of light is

required in particular localities, there ought to be placed near these

spots gasometers of distribution, which, being filled during the slack

hours of the day, are ready to supply the burners at night, without

making any considerable demand upon the original main pipe. Suppose the

first main be required to supply 8000 cubic feet in the hour, for an

illumination of 8 hours, at the distance of 2000 feet, a pipe 10-2/3

inches in diameter would be necessary; but if two or three gasometers of

distribution, or station gasometers be had recourse to, into which the

gas during the course of 24 hours would flow through the same distance

continuously from the central gas works, the quantity required per hour

from them would be only one third of 8000, = 2666·6 cubic feet;

consequently the diameter for such a pipe is only 6·15 inches.

[Illustration: 492]

All the principal as well as branch pipes, whose interior diameter

exceeds an inch and a half, are made of cast iron from 6 to 8 feet long,

with elbow pipes cast in them where it is necessary. These pipe lengths

are shown in _fig._ 492., having at one end a wide socket _a_, and at

the other a nozzle _b_, which fits the former. After inserting the one

in the other in their proper horizontal position, a coil of hemp soaked

with tar is driven home at the junction; then a luting of clay is

applied at the mouth, within which a ring of lead is cast into the

socket, which is driven tight home with a mallet and blunt chisel.

The pipes should be proved by a force pump before being received into

the gas works; two or three lengths of them should be joined before

laying them down, and they should be placed at least two feet below the

surface, to prevent their being affected by changes of temperature,

which would loosen the joints. The tubes for internal distribution, when

of small size are made of lead, copper, wrought iron, or tin.

[Illustration: 493]

Instead of a stopcock for letting off the gas in regulated quantities

from the gasometer, a peculiarly formed water or mercurial valve is

usually employed. _Fig._ 493. shows the mode of construction for a water

trap or lute, and is, in fact, merely a gasometer in miniature. C D E F

is a square cast iron vessel, in the one side of which a pipe A is

placed in communication with the gasometer, and in the other, one with

the main B. The movable cover or lid H G I K has a partition, L M, in

its middle. If this cover be raised by its counterweight, the gas can

pass without impediment from A to B; but if the counterweight be

diminished so as to let the partition plate L M sink into the water, the

communication of the two pipes is thereby interrupted. In this case the

water-level stands in the compartment A so much lower than outside of

it, and in the compartment B, as is equivalent to the pressure in the

gasometer; therefore the pipes A and B must project thus far above the

water. In order to keep the water always at the same height, and to

prevent it from flowing into the mouths of these pipes, the rim C D of

the outer vessel stands somewhat lower than the orifices A B; and thence

the vessel may be kept always full of water.

[Illustration: 494]

If a quicksilver valve be preferred, it may be constructed as shown in

_fig._ 494. A B are the terminations of the two gas pipes, which are

made fast in the rectangular iron vessel M. E is an iron vessel of the

same form, which is filled with quicksilver up to the level _a_, and

which, by means of the screw G, which presses against its bottom, and

works in the fixed female screw C C, may be moved up or down, so that

the vessel M may be immersed more or less into the quicksilver. The

vessel M is furnished with a vertical partition _m_; the passage of the

gas from A to B is therefore obstructed when this partition dips into

the quicksilver, and from the gradual depression of the vessel E by its

screw, the interval between the quicksilver and the lower edge of the

partition, through which the gas must enter, may be enlarged at

pleasure, whereby the pressure of the gas in B may be regulated to any

degree. The transverse section of that interval is equal to the area of

the pipe or rather greater; the breadth of the vessel M from A to B

amounts to the double of that space, and its length to the mere diameter

of A or B. The greatest height to which the partition _m_ can rise out

of the quicksilver, is also equal to the above diameter, and in this

case the line _a_ comes to the place of _b_. The vertical movement of

the outer vessel E, is secured by a rectangular rim or hoop which

surrounds it, and is made fast to the upper part of the vessel M, within

which guide it moves up and down. Instead of the lever D D, an index

with a graduated plate may be employed to turn the screw, and to

indicate exactly the magnitude in the opening of the valve.

[Illustration: 495]

In order to measure the quantity of gas which passes through a pipe for

lighting a factory, theatre, &c., the gas-meter is employed, of whose

construction a sufficiently precise idea may be formed from the

consideration of _fig._ 495., which shows the instrument in a section

perpendicular to its axis.

Within the cylindrical case _a_, there is a shorter cylinder _b b_, shut

at both ends, and movable round an axis, which is divided into four

compartments, that communicate by the opening _d_, with the interval

between this cylinder and the outer case. The mode in which this

cylinder turns round its axis is as follows:--The end of the tube _c_,

which is made fast to the side of the case, and by which the gas enters,

carries a pivot or gudgeon, upon which the centre of its prop turns; the

other end of the axis runs in the cover, which here forms the side of a

superior open vessel, in which, upon the same axis, there is a toothed

wheel. The vessel is so far filled with water, that the tube _c_ just

rises above it, which position is secured by the level of the side

vessel. When the gas enters through the tube _c_, by its pressure upon

the partition _e_, (_fig._ 495.) it turns the cylinder from right to

left upon its axis, till the exterior opening _d_ rises above the water,

and the gas expands itself in the exterior space, whence it passes off

through a tube at top. At every revolution a certain volume of gas thus

goes through the cylinder, proportional to its known capacity. The wheel

on the axis works in other toothed wheels, whence, by means of an index

upon a graduated disc or dial, placed at top or in front of the

gas-meter, the number of cubic feet of gas, which pass through this

apparatus in a given time, is registered.

B. _Employment of the gas for lighting._--The illuminating power of

different gases burned in the same circumstances, is proportional,

generally speaking, to their specific gravity, as this is to the

quantity of carbon they hold in combination. The following table

exhibits the different qualities of gases in respect to illumination.

+-------------------+----------------------------+

| Density or |Proportion of light afforded|

| specific gravity. | by coal gas to oil gas. |

+----------+--------+----------------------------+

| Coal gas.|Oil gas.| |

+----------+--------+ |

| 0·659| 0·818 | 100 : 140 |

| 0·578| 0·910 | 100 : 225 |

| 0·605| 1·110 | 100 : 250 |

| 0·407| 0·940 | 100 : 354 |

| 0·429| 0·965 | 100 : 356 |

| 0·508| 1·175 | 100 : 310 |

+----------+--------+----------------------------+

|Mean 0·529| 0·96 | 100 : 272 |

+----------+--------+----------------------------+

In the last three proportions, the coal gas was produced from coals of

middle quality; in the first three proportions from coals of good

quality; and therefore the middle proportion of 100 to 270 may be taken

to represent the fair average upon the great scale. On comparing the gas

from bad coals, with good oil gas, the proportion may become 100 to 300.

Nay, coal gas of specific gravity 0·4, compared to oil gas of 1·1, gives

the proportion of 1 to 4. A mould tallow candle, of 6 in the pound,

burning for an hour, is equivalent to half a cubic foot of ordinary coal

gas, and to four tenths of a foot of good gas. The flame of the best

argand lamp of Carcel, in which a steady supply of oil is maintained by

pump-work, consuming 42 grammes = 649 grains English in an hour, and

equal in light to 9·38 such candles, is equivalent to 3·75 cubic feet of

coal gas per hour. The sinumbra lamp, which consumes 50 grammes = 772

grains English, of oil per hour, and gives the light of 8 of the above

candles, is equivalent to the light emitted by 3·2 cubic feet of coal

gas burning for an hour. A common argand lamp, equal to 4 candles, which

consumes 30 grammes = 463 grains English per hour, is represented by 1·6

cubic feet of gas burning during the same time. A common lamp, with a

flat wick and glass chimney, whose light is equal to 1·13 tallow

candles, and which consumes 11 grammes = 169·8 grains English per hour,

is represented by 0·452 of a cubic foot of gas burning for the same

time.

_Construction of the Burners._--The mode of burning the gas as it issues

from the jets has a great influence upon the quantity and quality of its

light. When carburetted hydrogen gas is transmitted through ignited

porcelain tubes, it is partially decomposed with a precipitation of some

of its carbon, while the resulting gas burns with a feebler flame. Coal

gas, when kindled at a small orifice in a tube, undergoes a like

decomposition and precipitation. Its hydrogen, with a little of its

carbon, burns whenever it comes into contact with the atmospherical air,

with a bluish coloured flame; but the carbonaceous part not being so

accendible, takes fire only when mixed with more air; therefore at a

greater distance from the beak, and with a white light from the vivid

ignition of its solid particles. Upon this principle pure hydrogen gas

may be made to burn with a white instead of its usual blue flame, by

dusting into it particles of lamp black; or by kindling it at the

extremity of a tube containing finely pulverized zinc. The metallic

particles become ignited, and impart their bright light to the pale blue

flame. Even platinum wire and asbestos, when placed in the flame of

hydrogen gas, serve to whiten it. Hence it has been concluded, that the

intensity of light which a gas is capable of affording is proportional

to the quantity of solid particles which it contains, and can

precipitate in the act of burning. Carbonic oxide gas burns with the

feeblest light next to hydrogen, because it deposits no carbon in the

act of burning. Phosphuretted hydrogen gives a brilliant light, because

the phosphoric acid, into which its base is converted during the

combustion, is a solid substance, capable of being ignited in the flame.

Olefiant gas, as also the vapour of hydro-carbon oil, emits a more vivid

light than common coal gas; for the first is composed of two measures of

hydrogen and two measures of the vapour of carbon condensed into one

volume; while the last contains only one measure of the vapour of carbon

in the same bulk, and combined with the same proportion of hydrogen.

Olefiant gas may therefore be expected to evolve a double quantity of

carbon in its flame, which should emit a double light.

The illuminating power of the flame of coal gas is, on the contrary,

impaired, when, by admixture with other species of gas which precipitate

no carbon, its own ignited particles are diffused over a greater

surface. This happens when it is mixed with hydrogen, carbonic oxide,

carbonic acid, and nitrogen gases, and the diminution of the light is

proportional to the dilution of the coal gas.

[Illustration: 496 497]

In like manner the illuminating power of coal gas is impaired, when it

is consumed too rapidly to allow time for the separation and ignition of

its carbonaceous matter; it burns, in this case, without decomposition,

and with a feeble blue flame. 1. This occurs when the light-gas is

previously mixed with atmospherical air, because the combustion is

thereby accelerated throughout the interior of the flame, so as to

prevent the due separation of carbon. A large admixture of atmospherical

air makes the flame entirely blue. 2. When it issues, with considerable

velocity, from a minute orifice, whereby the gas, by expansion, gets

intimately mixed with a large proportion of atmospherical air. If the

jet be vertical, the bottom part of the flame is blue, and the more so

the less carbon is contained in the gas. The same thing may be observed

in the flame of tallow, wax, or oil lights. The burning wick acts the

part of a retort, in decomposing the fatty matter. From the lower part

of the wick the gases and vapours of the fat issue with the greatest

velocity, and are most freely mixed with the air; while the gases

disengaged from the upper part of the wick compose the interior of the

flame, and being momentarily protected from the action of the

atmosphere, acquire the proper high temperature for the deposition of

carbon, which is then diffused on the outer surface in an ignited state,

and causes its characteristic white light. Hence with coal gas, the

light increases in a certain ratio with the size of the flame as it

issues from a larger orifice, because the intermixture of air becomes

proportionately less. 3. If by any means too great a draught be given to

the flame, its light becomes feebler by the rapidity and completeness

with which the gas is burned, as when too tall a chimney is placed over

an argand burner, see _fig._ 496. _Fig._ 497. _c_, is a view of the

upper plate, upon which the glass chimney _b_ rests. The gas issues

through the smaller openings of the inner ring, and forms a hollow

cylindrical flame, upon the outside as well as the inside of which the

atmospherical air acts. The illuminating power of this flame may be

diminished at pleasure, according as more or less air is allowed to

enter through the orifices beneath. With a very full draught the light

almost vanishes, leaving only a dull blue flame of great heating power,

like that of the blowpipe, corresponding to the perfect combustion of

the gas without precipitation of its carbon. 4. On the other hand, too

small a draught of air is equally prejudicial; not merely because a

portion of the carbon thus escapes unconsumed in smoke, but also because

the highest illuminating power of the flame is obtained only when the

precipitated charcoal is heated to whiteness, a circumstance which

requires a considerable draught of air. Hence the flame of dense oil

gas, or of oil in a wick, burns with a yellow light without a chimney;

but when it is increased in intensity by a chimney draught, it burns

with a brilliant white flame.

From the consideration of the preceding facts, it is possible to give to

coal gas its highest illuminating power. The burners are either simple

beaks perforated with a small round hole, or circles with a series of

holes to form an argand flame, as shown in _fig._ 497, or two holes

drilled obliquely, to make the flame cross, like a swallow’s tail, or

with a slit constituting the sheet of flame called a bat’s wing, like

most of the lamps in the streets of London. These burners are mounted

with a stop-cock for regulating the quantity of gas.

The height of the flame, which with like pressure depends upon the size

of the orifice, and with like orifice upon the amount of pressure, the

latter being modified by the stop-cock, is for simple jets in the open

air, as follows:--

Length of the flame 2 3 4 5 6 inches

Intensity of the light 55·6 100 150 197·8 247·4

Volume of gas consumed 60·5 101·4 126·3 143·7 182·2

Light with equal consumption 100 109 131 150 150

When the length exceeds five inches, nothing is gained in respect to

light. For oil gas the same statements will serve, only on account of

its superior richness in carbon, it does not bear so long a flame

without smoke. Thus:--

Length of the flame 1 2 3 4 5 inches

Intensity of the light 22 63·7 96·5 141 178

Gas consumed 33·1 78·5 90 118 153

Light with equal consumption 100 122 159 181 174

The diameter of the orifice for single jets, or for several jets from

the same beak, is one twenty-eighth of an inch for coal gas, and one

forty-fifth for oil gas.

[Illustration: 498 499]

When several jets issue from the same burner, the light is improved by

making all the flames unite into one. In this case the heat becomes

greater, for the combined flame presents a smaller surface to be cooled,

than the sum of the smaller flames. The advantage gained in this way,

may be in the ratio of 3 to 2, or 50 per cent. In an argand burner, the

distances of the orifices for coal gas should be from 16/100 to 18/100

of an inch, and for oil gas 12/100. If the argand ring has ten orifices,

the diameter of the central opening should be = 4/10 of an inch; if 25

orifices, it should be one inch for coal gas; but for oil gas with 10

orifices, the central opening should have a diameter of half an inch,

and for 20 orifices, one inch. The pin holes should be of equal size,

otherwise the larger ones will cause smoke, as in an argand flame with

an uneven wick. The glass chimney is not necessary to promote the

combustion of an argand coal gas flame, but only to prevent it from

flickering with the wind, and therefore it should be made so wide as to

exercise little or no influence upon the draught. A narrow chimney is

necessary merely to prevent smoke, when a very strong light, with a

profusion of gas is desired. Oil gas burned in an argand beak requires a

draught chimney, like a common argand lamp, on account of the large

quantity of carbon to be consumed. The most suitable mode of regulating

the degree of draught can be determined only by experiment, and the best

construction hitherto ascertained is that represented in _fig._ 498.

_Fig._ 499. exhibits the view from above, of the rim or ring _c_, upon

which the chimney _b_ stands, and which surrounds the perforated beak.

The ring is made of open fretwork, to permit the free passage of air

upwards to strike the outside of the flame. The thin annular disc _d_,

which is laid over its fellow disc _c_, in the bottom of the

chimney-holder, being turned a little one way or other, will allow more

or less air to pass through for promoting more or less, the draught or

ventilation. The draught in the central tube of the burner may be

regulated by the small disc _e_, whose diameter is somewhat smaller than

that of the ring of the burner, and which by turning the milled head

_f_, of the screw, may be adjusted with the greatest nicety, so as to

admit a greater or smaller body of air into the centre of the

cylindrical flame.

In mounting gas-lights, and in estimating beforehand their illuminating

effects, we must keep in mind the optical proposition, that the quantity

of light is inversely as the square of the distance from the luminous

body, and we must distribute the burners accordingly. When for example a

gas-light placed at a distance of ten feet, is required for reading or

writing to afford the same light as a candle placed at a distance of two

feet; squaring each distance, we have 100 and 4; therefore 100/4 = 25,

shows us that 25 such lights will be necessary at the distance of 10

feet.

Concerning portable gas-light, with the means of condensing it, and

carrying it from the gas works to the places where it is to be consumed,

we need say nothing, as by the improvements lately made in the

purification and distribution of coal-gas, the former system has been

superseded.

It is well known that light gas deteriorates very considerably by

keeping, especially when exposed to water over an extensive surface; but

even to a certain degree over oil, or in close vessels. An oil-gas which

when newly prepared has the specific gravity of 1·054, will give the

light of a candle for an hour, by consuming 200 cubic inches; will,

after two days, give the same light by consuming 215 cubic inches per

hour; and after four days, by consuming 240 cubic inches in the like

time. With coal-gas the deterioration appears to be more rapid. When

newly prepared, if it affords the light of a candle with a consumption

of 400 cubic inches per hour; it will not give the same light after

being kept two days, except with a consumption of 430 inches; and after

four days, of 460. Oil-gas three weeks old has become so much impaired

in quality that 600 inches of it were required per hour to furnish the

light of a candle. All light gas should be used therefore as soon as

possible after it is properly purified.

_Economical considerations._--The cost of gas-light depends upon so many

local circumstances, that no estimate of it can be made of general

application; only a few leading points may be stated. The coals

required for heating the retorts used to constitute one half of the

quantity required for charging the retorts themselves. When five retorts

are heated by one fire, the expenditure for fuel is only one third of

that when each retort has a fire. The coak which remains in the retorts

constitutes about 60 per cent. of the weight of the original coal; but

the volume is increased by the coaking in the proportion of 100 to 75.

When the coak is used for heating the retorts, about one half of the

whole is required. If we estimate the coak by its comparative heating

power, it represents 65 per cent. of the coals consumed. One hundred

pounds of good coal yield in distillation 10 pounds of ammoniacal

liquor, from which sulphate or muriate of ammonia may be made, by

saturation with sulphuric or muriatic acid, and evaporation. The liquor

contains likewise some cyanide of ammonia, which may be converted into

prussian blue by the addition of sulphate of iron, after saturation with

muriatic acid.

Two hundred pounds of coal afford about 17 pounds of tar. This contains

in 100 pounds 26 pounds of coal oil, and 48 pounds of pitch. The tar is

sometimes employed as a paint to preserve wood and walls from the

influence of moisture, but its disagreeable smell limits its use. The

coal oil when rectified by distillation, is extensively employed for

dissolving caoutchouc in making the varnish of waterproof cloth, and

also for burning in a peculiar kind of lamps under the name of naphtha.

Oil of turpentine however is often sold and used for this purpose, by

the same name. If the coal oil be mixed with its volume of water, and

the mixture be made to boil in a kettle, the mingled vapours when passed

through a perforated nozzle may be kindled, and employed as a powerful

means of artificial heat. The water is not decomposed, but it serves by

its vapour to expand the bulk of the volatile oil, and to make it

thereby come into contact with a larger volume of atmospherical air, so

as to burn without smoke, under a boiler or any other vessel. The pitch

may be decomposed into a light-gas.

The relative cost of light from coal gas and oil gas may be estimated as

one to six, at least. Rosin gas is cheaper than oil gas. See ROSIN.

I shall conclude this article with a summary of the comparative expense

of different modes of illumination, and some statistical tables.

One pound of tallow will last 40 hours in six mould candles burned in

succession, and costs 8_d._; a gallon of oil, capable of affording the

light of 15 candles, for 40 hours costs 5_s._, being therefore 1/2 of

the price of mould candles, and 6/15 of the price of dips. The cost of

wax is about 3-1/2 times that of tallow; and coal gas, as sold at the

rate of 9_s._ for 1000 cubic feet, will be one sixth the price of mould

candles; for 500 cubic inches of coal gas give a light equal to the

above candle for an hour; therefore 40 × 500 = 20,000 cubic inches =

11·57 cubic feet, worth 1-1/4_d._, which multiplied by 6 gives 7-1/2_d._

the average price of mould candles per pound.

The author of the article _Gas-light_ in the Encyclopædia Britannica,

observes, in reference to the economy of this mode of illumination, that

while the price of coal, in consequence of the abundant and regular

supply of that article, is liable to little fluctuation, the cost of

wax, tallow, and oil, on account of the more precarious nature of the

sources from which they are obtained, varies exceedingly in different

seasons. “Assuming that a pound of tallow candles, which last when

burned in succession forty hours, costs nine-pence,” (seven-pence

halfpenny is the average price), “that a gallon of oil, yielding the

light of 600 candles for an hour, costs two shillings,” (five shillings

is the lowest price of a gallon of such oil as a gentleman would choose

to burn in his lamp), “that the expense of the light from wax is three

times as great as from tallow, and that a thousand cubic feet of coal

gas cost nine shillings;” he concludes the relative cost to be for the

same quantity of light,--from wax, 100; tallow, 25; oil, 5; and

coal-gas, 3. I conceive the estimate given above to be much nearer the

truth; when referred to wax called 100, it becomes, for tallow, 28·6;

oil, 14·3; coal gas, 4·76.

Gas-lighting has received a marvellous development in London. In the

year 1834, the number of gas lamps in this city was 168,000, which

consumed daily about 4,200,000 cubic feet of gas. For the purpose of

generating this gas, more than 200,000 chaldrons, or 10,800,000 cubic

feet of coals were required.

For the following valuable statistical details upon gas-light, my

readers are indebted to Joseph Hedley, Esq., engineer, of the Alliance

Gas Works, Dublin; a gentleman who to a sound knowledge of chemistry,

joins such mechanical talent and indefatigable diligence, as qualify him

to conduct with success, any great undertaking committed to his care. He

has long endeavoured to induce the directors of the London gas-works to

employ a better coal, and generate a more richly carburetted gas, which

in much smaller quantity would give as brilliant a light, without

heating the apartments unpleasantly, as their highly hydrogenated gas

now does. Were his judicious views adopted, coal gas would soon

supersede oil, and even wax candles, for illuminating private mansions.

Copy of a paper laid before a Committee of the House of Commons, showing

not only the relative values of the Gases produced at the undermentioned

places, but showing in like manner the relative economy of Gas as

produced at the different places, over candles. By Joseph Hedley, Esq.

+---------------+---------------------------------------------------+

|Names of the |Illuminating power of a single Jet of Gas-flame |

|Places where |four inches high, taken by a comparison of Shadows.|

|Experiments | +-----------------------------------------+

|were made. | |The Jet of Gas burnt, four inches high, |

| | |consumed per hour and was equal to the |

| | |Candles in the last column. |

| | | +----------------------------------+

| | | | +---------------------------+

+---------------+---------+------+------+-------+-------------------+

|Birmingham; }| | | | |

|Birmingham and}| | | | |

|Staffordshire;}| 2·572 | 1·22 | 2704 |10 0 |

|two Companies }| | | | |

|Stockport | 3·254 | ·85 | 1489 |10 0 |

|Manchester | 3·060 | ·825| 1536 | 8 0 |

|Liverpool Old}| | | | |

|Company[C] }| 2·369 | 1·1 | 2646 |10 0 |

|Liverpool New} | | | | |

|Gas Company } | 4·408 | ·9 | 1164 |10 0 |

|Bradford | 2·190 | 1·2 | 3123 | 9 0 |

|Leeds | 2·970 | ·855| 1644 | 8 0 |

|Sheffield | 2·434 | 1·04 | 2440 | 8 0 |

|Leicester | 2·435 | 1·1 | 2575 | 7 6 |

|Nottingham | 1·645 | 1·3 | 4200 | 9 0 |

|Derby | 1·937 | 1·2 | 3521 |10 0 |

|Preston | 2·136 | 1·15 | 3069 |10 0 |

| | | | | |

|London | 2·083 | 1·13 | 3092 |10 0 |

+---------------+---------+------+------+-------+

+---------------+---------------------------------------------------+

|Names of the |Cost of Gas equal in illuminating power to 100 lbs.|

|Places where |of candles.[B] |

|Experiments | +----------------------------------------+

|were made. | |Average discount allowed off the charge |

| | |for Gas. |

| | | +-------------------------------+

| | | | +--------------------+

+---------------+----------+--------+----------+----+---------------+

| | | _Per_ | | |

| |_L. s. d._|_Cent._ |_L. s. d._| |

|Birmingham; }| | | | |

|Birmingham and}| | | | |

|Staffordshire;}| 1 7 0 | 9 | 1 4 7 |·541|

|two Companies }| | | | |

|Stockport | 0 14 11 | 12-1/2 | 0 13 0 |·539|

|Manchester | 0 12 3 | 11-1/4 | 0 0 10 |·534|

|Liverpool Old}| | | | |

|Company[C] }| 1 6 5 | 6-1/4 | 1 4 9 |·462|

|Liverpool New} | | | | |

|Gas Company } | 0 11 8 | 6-1/4 | 0 9 10 |·580|

|Bradford | 1 8 1 | 12-1/2 | 1 4 6 |·420|

|Leeds | 0 13 2 | 6-1/4 | 0 12 4 |·530|

|Sheffield | 0 19 6 | 6-1/4 | 0 18 3 |·466|

|Leicester | 0 19 3 | 15 | 0 16 5 |·528|

|Nottingham | 1 17 9 | 15 | 1 11 3 |·424|

|Derby | 1 15 4 | 15 | 1 10 0 |·448|

|Preston | 1 10 8 | 15 | 1 6 2 |·419|

|London | 1 10 11 |allowed.| 1 10 11 |·412|

+---------------+----------+--------+----------+----+

[A] 100 lbs. of candles are estimated to burn 5700 hours.

[B] The candles cost 3_l._ 2_s._ 6_d._

[C] The Liverpool Old Company have since resorted to the use of

Cannel coal, and consequently very nearly assimilate to the

Liverpool New Company in illuminating power.

MEMORANDUM.--It will not fail to be observed that in deducing the

comparative value between candles and gas by these experiments, the

single jet (and in every instance, of course, it was the same), has

been the medium. This however, though decidedly the most correct way

of making the comparative estimate of the illuminating power of the

several gases, is highly disadvantageous in the economical comparison,

inasmuch as gas burnt in a properly regulated argand burner, with its

proper sized glass, air aperture, and sufficient number of holes,

gives an advantage in favour of gas consumed in an argand, over a jet

burner, of from 30 to 40 per cent. At the same time it must not be

overlooked that in many situations where great light is not required,

it will be found far more economical to adopt the use of single jets,

which by means of swing brackets and light elegant shades, becomes

splendid substitutes for candles, in banking establishments, offices,

libraries, &c. &c.

NOTE.--In Glasgow, Edinburgh, Dundee, Perth, and the Scotch towns

generally the Parrot or Scotch Cannel coal is used; in illuminating

power and specific gravity the gas produced is equal to that from the

best description of Cannel coal in England. The price per 1000 cubic

feet ranges about 9_s._, with from 5 to 30 per cent. off for

discounts, leaving the net price about 9_s._ to be equal in the above

table to 100 lbs. of candles.

Epitome of Experiments made in Gas produced from different qualities of

Coal, and consumed in different kinds of Burners:

Tried at the Sheffield Gas Light Company’s Works, and laid before a

Committee of the House of Commons. By Joseph Hedley, Esq.

+------+-----------+----------+--------+---------+--------+-------+

| | | | | | | |

| | | | | | | |

+------+-----------+----------+--------+---------+--------+-------+

| | | | | |_Cubic_ | _In-_ |

| 8 | Single Jet|Deep Pit | ·410 | 75 | 1· |4 |

| 9 | Ditto |Mortormley| ·450 | 74 | ·95 |4 |

| 9 | Ditto |Cannel | ·660 | 61-1/4 | ·7 |4 |

| 8 |{ Argand }| | | | | |

| |{ 14 holes}|Deep Pit | ·410 | 34 | 3·3 |3-1/2 |

| 9 | Ditto |Mortormley| ·450 | 33 | 3·1 |3-1/2 |

| 9 | Ditto |Cannel | ·660 | 29 | 2·6 |3-1/3 |

+------+-----------+----------+--------+---------+--------+-------+

+------+-------------+-----------+------------+----------+

+------+-------------+-----------+------------+----------+

|_May._| _Candles._ | _Feet._ |_L. s. d._ |_L. s. d._|

| 8 | 2·36 | 2415 | 0 19 3-1/2}| |

| 9 | 2·434 | 2224 | 0 17 9-1/2}| |

| 9 | 3·54 | 1127 | 0 9 0 }| |

| 8 | | | }| 3 2 6 |

| | 11·53 | 1631 | 0 13 0-1/2}| |

| 9 | 12·24 | 1443 | 0 11 6-1/2}| |

| 9 | 15·85 | 935 | 0 7 5-3/4}| |

+------+-------------+-----------+------------+----------+

Copy of Experiments made at the Alliance Gas Company’s Works in Dublin,

during the past year 1837. By Joseph Hedley, Esq.

Results of experiments on the qualities of various coals for the

production of gas; its value in illuminating power; produce of coke, and

quality; and other particulars important in gas-making:--

_1st Experiment, Saturday, May 27th, 1837._--Deane coal, (Cumberland). 2

cwt. of 112 lbs. each (or 224 lbs.) produced 970 cubic feet of gas; 4

bushels of coke of middling quality; specific gravity of the gas, 475.

Consumed in a single-jet burner, flame 4 inches high, 1-4/10ths cubic

feet per hour; distance from shadow 76 inches or 2·3 mould candles.

Average quantity of gas made from the charge (6 hours) 4·33 cubic feet

per lb., or 9,700 cubic feet per ton of 20 cwt. Increase of coke over

coal in measure, not quite 30 per cent. Loss in weight between coal,

coke and breize 56 lbs., converted into gas, tar, ammonia, &c.

_2nd Experiment, May 28th._--Carlisle coal, (Blenkinsopp). 224 lbs.

produced 1010 cubic feet of gas, 4 bushels of coke of good quality

though small; increase of coke over coal in measure not quite 30 per

cent. Loss in weight, same as foregoing experiment. Average quantity of

gas made from the charge (6 hours) 4·5 cubic feet per lb. or 10,080 per

ton.

_Illuminating power of the Gas._

+-------------------------------+---------+--------+--------+--------+

| |jet. | | | |

+-------------------------------+---------+--------+--------+--------+

| | _feet._ | _in-_ | | |

|At the end of the 1st hour | 1-1/10 | 70 | 2·72 | ·475 |

|Ditto ditto with 20-hole}| | | | |

|argand burner }| 5 | 25 | 21·33 | ·475 |

|When charge nearly off | 1-4/10 | 85 | 1·84 | ·442 |

|When charge quite off, with }| | | | |

|20-hole argand burner }| 9 | 100 | not 1 | ·256 |

+-------------------------------+---------+--------+--------+--------+

_3rd Experiment, May 29th._--Carlisle coal (Blenkinsopp). 112 lbs.

produced 556 cubic feet of gas. Other products, loss of weight, &c.,

same proportion as foregoing experiment. Average quantity of gas made

from the charge (6 hours) 4·96 cubic feet per lb., or 11,120 per ton.

In this experiment the quantity of gas generated every hour was

ascertained; the illuminating power, the specific gravity, and the

quantity of gas consumed by the single jet with a flame 4 inches high,

was tried at the end of each hour, with the respective gases generated

at each hour; and the following is a table of results.

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