MAN'L'FACTUKING COAL GAS IN LONDON. 101

of furnishing, because by so doing the retortsbecome less deteriorated and remain for a longertime in a state fit for use.

The quantity of gas to be supplied each night,was, as in the preceding process, fifty thousandcubic feet.

The number of retorts required to produce thatquantity, was forty-two, and to make them lasttwelve months instead of six months, as in thepreceding process, it was necessary to work themat a temperature, at which a chaldron of coalproduces from seven thousand, to eight thousandcubic feet of gas.

The result of this operation was as follows :

Cost of forty-two retorts, withbrick-Avork foundation, cast-iron cokehearth, perpendicular dip pipe, con-nected with the hydraulic main, at£.23 each. £. 966 0 0

Eight workmen, four by day andfour by night, at £ 1 . 6s. each the Aveek £.540 16 0

Carried over <£.1506 16 0