| London Chaldrons | |
| The total consumption of coal from the rivers Tyne and Wear known from the register to be | 2,300,000 |
| The number of tons in the above quantity taking the London chaldron at 27 cwt. is | 3,100,000 |
| Now a ton weight of coal is estimated to occupy in the earth the space of one cubic yard. | |
| The number of cubic yards in the square mile is | 3,097,600 |
| The beds or seams of coal are, on an average, 4 feet and a half in thickness, which increases the above number of cubic yards in the square mile by half the number of square yards to | 1,548,800 |
| And hence the square mile of the beds or seams of coal we are describing contains, of cubic yards and tons of coal | 4,645,000 |
| A deduction of 1-6th for pillars to support the mine, &c. | 800,000 |
| The number of tons per square mile | 5,445,000 |
We have already mentioned the length and breadth of the seams of coal to be equal to 20 miles by 15, making an area of 300 square miles, and consequently a source of consumption for 375 years.
It may be objected to the universality of our conclusion, that the price of coals, differing very much in different places, will occasion a variation in the expence of the new mode of illumination. But there are two reasons why this should have less place, because we find, in Mr. Murdoch’s statement, [page 69], that of 600l. the estimated yearly expence of lighting the cotton mill, 550l. consist of interest of capital, and tear and wear of apparatus, leaving the cost of coal only 50l. a sum so trifling, when we reflect that it replaces 2000l. worth of candles, that the price of coal, even where it is highest, can but slightly affect the general profits.[32]
[32] See, also, Mr. Ackermann’s statement, [page 71].
2dly, The coal, by yielding the gas and other products,—namely, tar, pitch, ammoniacal liquor, &c. of which we have treated already, is converted into a substance, increased in bulk, and in the power of producing heat, namely, coke; and as a manufactory generally requires heating as well as lighting, there will be a gain both ways. The manufacturer, by distilling his coal, instead of burning it as it comes from the pit, will save his candles and improve his fuel. One effort at the outset, in erecting a proper apparatus, will reduce his annual disbursement, for these two articles of prime necessity, much in the same manner, (though in a far greater degree) as the farmer gains by building a thrashing machine and laying aside the use of the flail.
The principal expence in the pursuit of this branch of civil and domestic economy is therefore the dead capital employed in erecting the machinery destined for preparing and conveying the gas; the floating or live capital is comparatively small. At the same time, were we to offer an advice to the public on this subject, it would be, that no private individual resident in London should attempt to light his premises for the sake of economy with coal-gas by means of his own apparatus, whose annual expence for light does not exceed 60l. because the expence of erecting and attending a small apparatus is almost as great as one constructed on a larger scale would be. For if the quantity of gas wanted is not sufficient to keep the retorts continually in a red-hot or working state, the cost of the gas will be considerably enhanced; because either the empty retorts must be continued red-hot, or the fire must be suffered to go out; and the retorts, when cold, cannot be brought to a working state, that is to say, be made red hot again, but at a considerable expence of fuel, which must be wasted to no purpose. Whereas, if the retorts are constantly kept red hot and in action, one half of the coal necessary to produce a given quantity of gas will then be saved. But when a street, or a small neighbourhood is wanted to be lighted, and the retorts can always be kept in a working state, that is to say, red hot, the operation may be commenced with safety; because the sum required for erecting the apparatus, and the labour attending it, together with the interest of money sunk, will then soon be liquidated by the light which it will afford.
Individuals, therefore, may engage in the distillation of coal, and trade with advantage in the articles produced by that process, and the lighting of cities may be accomplished without the aid of incorporated bodies; and parishes may be lighted by almost as many individuals as there are streets in a parish.
From experiments, made by Mr. Clegg, on the effects produced by a number of gas-lights, of a certain intensity, there is reason to believe that the streets of small towns might be illuminated at a cheaper rate, by means of a tower, or pagoda, furnished with gas-lamps, than can be done in the ordinary way by street lamps: the gas being conducted to the top of the building from the apparatus below, and the light directed down again, upon the objects to be illuminated, by means of reflectors placed at a certain angle. By this contrivance, all the main pipes which convey the gas through the streets, as well as those collateral ones that branch out from them to the street lamps, would be saved, and thus compensate for the expense of the tower.
The most beneficial application of gas-lights unquestionably is in all those situations where a great quantity of light is wanted in a small place: and where light is required to be most diffused, the advantages of this mode of illumination are the least.—Hence, as already stated, the lighting of the parish, or street-lamps only, without lighting shops or houses, can never be accomplished with economy.