A TRETISE ON GAS-tlGHt,

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Cessity, much in the same manner, (though ina far greater degree) as the farmer gains bybuilding a thrashing machine and laying asidethe nse of the flaih

The principal expence in the pursuit of thisbranch of civil and domestic economy is there-fore the dead capital employed in erecting themachinery destined for preparing and convey-ing the gas ; the floating or live capital is com-paratively small. At the same time, were weto offer an ad% ice to the public on this subject,it would be, that no private individual residentin London should attempt to light his premisesfor the sake of economy with coal-gas by meansof his own apparatus, whose annual expencefor light does not exceed 6ol. because the ex-pence of erecting and attending a small appa-ratus is almost as great as one constructed on alarger scale would be. For if the quantity ofgas wanted is not sufficient to keep the retortscontinually in a red-hot or- working state, thecost of the gas will be considerably enhanced ;because either the empty retorts must be con-tinued red-hot, or the fire must be suffered togo out; and the retorts, when cold, cannot be

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