The more important advantages of acetylene as an illuminant have now been indicated, and it remains to discuss the cost of acetylene lighting in comparison with other modes of procuring artificial light. At the outset it may be stated that a very much greater reduction in the price of calcium carbide--from which acetylene is produced--than is likely to ensue under the present methods and conditions of manufacture will be required to make acetylene lighting as cheap as ordinary gas lighting in towns in this country, provided incandescent burners are used for the gas. On the score of cheapness (and of convenience, unless the acetylene were delivered to the premises from some central generating station) acetylene cannot compete as an illuminant with coal-gas where the latter costs, say, not more than 5s. per 1000 cubic feet, if only reasonable attention is given to the gas-burners, and at least a quarter of them are on the incandescent system. If, on the other hand, coal-gas is misused and wasted through the employment only of interior or worn-out flat-flame burners, while the best types of burner are used for acetylene, the latter gas may prove as cheap for lighting as coal-gas at, say, 2s. 6d. per 1000 cubic feet (and be far better hygienically); whereas, contrariwise, if coal-gas is used only with good and properly maintained incandescent burners, it may cost over 10s. per 1000 cubic feet, and be cheaper than acetylene burned in good burners (and as good from the hygienic standpoint). More precise figures on the relative costs of coal-gas lighting and acetylene lighting are given in the tabular statement at the close of this chapter.