118 
Ges Lights. the gas to the place where it communicates with the 
burner. The pipes in the streets are laid so near the 
surface, as not to be disturbed by the carriages, or in- 
terfere with the paving. They are joined together by 
slipping one end of one into a widened part in the end 
of another. The cavity between the inside of one, and 
the outside of the other, which is nearly one inch, is 
filled with melted lead, which when set, is afterwards 
hammered in by the end of a punch. 
Having generally described the apparatus used: in 
lighting by gas, we shall give some statements respecting 
its economy compared with other means of lighting. 
Mr Murdoch, of whom we have before spoken, has 
published a statement of the expence of gas lighting, 
compared with candles, in the Philosophical Transac- 
tions of London, for the year 1808. He begins by as- 
certaining that a tallow candle, of six in the pound, 
is consumed at the rate of 175 grains, or 1.4 of an 
ounce in one hour; and that half a cubic foot of car 
He found, that to produce this gas, there was required 110 tons of cannel coal at 22s. 6d. per ton, £124 0 0 
Consumption of common coal for distilling the gas, 40 tons, at 10s... . . é s - 20 0 O 
Interest of the capital, and wear and tear of the apparatus, : ‘ : : 4 : - 550 0 0 
Total expence . £694 0 
Deduct the value of 70 tons of coak, ; : 3 3 : - - Sesh a 
Then deducting ‘ “ ° A ‘ . 
Leaves the clear annual saving 
0 
0 
Phe! Fla 
The price of 2,347,500 candles, equal to 891,2501b. at 1s.per lb. . I d 3 > £2000 0 
: 0 
0 
0 
If the working time per day were three hours, the annual saving ‘wouldthenbe =. 
The veracity of this author would alone be sufficient 
to give great weight to these facts; but they have 
gained greater strength by their strict agreement with 
subsequent experience. 
It is now found that the best form for the retorts is a 
eylinder, and that they should not much exceed 10 
inches in diameter, nor be much more than six feet in 
length. If they were much wider, the heat would not 
penetrate the loose coal within sufficiently ; and as re- 
gards the length, the fire would not act to much ad- 
vantage, nor the heat be uniform, if the length were 
much beyond the above statement. This should be the 
limit for one furnace. If more gas is wanted, more 
furnaces must be made, as has been shewn in the 
Plate. 
In an ao on the scale of these in London for 
lighting the streets, from 24 to 36 such retorts and fur- 
naces would be required. These retorts contain, inde» 
pendent of the mouth-pieces, about 5655 cubic inches, 
and will hold conveniently 100 1b. of cannel coal. When 
the fire is applied to good advantage, each retort gives 
out all its gas in about four hours, There is no good 
policy in pushing the distillation very far, as the gas 
which comes the last, is the least combustible. the 
retort should not be heated beyond a brightish red, as 
the gas is not only injured, but the retort would soon 
be destroyed, 
GAS LIGHTS. . 
buretted hydrogen, such as comes from cannel coal, 
burnt the same time, producing a light of the same 
intensity. We - 
In the calculation of the expence of lighting: 
he takes his estimate from the eaters of jee 
Lee and Philips of Manchester, the apparatus being 
put up by himself, He employed 271 Argand bun. 
ers, each being equal to four candles of the size above- 
mentioned, and 633 cockspur burners, each being equal 
to 2} candles, the whole amount being equal to 2500 } 
candles of the same size. From what has been stated, 
it will appear, that tokeep so many lights up, will re« 
quire an hourly consumption of 1200 cubic feet of 
He states the average time of working by the 
light throughout the year at two hours per day, thi 
will require a daily consumption of gas equal to 2500 — 
cubic feet ; and allowing 313 working days, the yearly 
consumption will be 782,500 cubic feet. 
Murdoch for the comparative light given by gas and 
candles, the gas and coak afforded from a given quan- 
tity of coal, and the consumption of common coal to ; 
produce the necessary heat for the distillation. The 
ion of tar and ammoniacal liquor we have : 
a teen Mr Accum’s work on gas Tights, ft 
The first column gives the number of retorts, each 
being 10 inches in diameter, and 6 feet long. The se- tion 
cond column gives the capacity of the gazometer. The T 
third column, the wei of coal used to furnish the 
gas. The fourth and fifth columns give the same by 
measure. The sixth, the coal used to distil off the 
The seventh, the cubic feet of purified gas. T i 
eighth, the weight of coak left in the retorts, T : 
ninth, the weight of tar. The tenth, the ammoniacal 
: 
; 
liquor ; and the eleventh, the number of candles: to 
produce the same light with the gas ; the candles being | 
six to the pound each, when fairly burnt, consuming _ 
175 grains of tallow in one hour. “vary i 
This Table is formed by doubling the first numbers of 
each column for the second number, then adding the 
first number to the second for the third, the thirdte _ 
the first for the fourth, and so on, so that it maybe 
easily extended to any greater number of retorts. 4 
