A TREATISE ON GAS-LIGHT.

m

a given time: it was found that we must burnof wax loo, of tallow 101 , of oil, in an Ar-gand’s lamp, 129 , of an ill-snuffed tallowcandle 22Q parts, by weight. And with re-gard to the quantity of carburetted hydrogen,or coal-gas, I have found that from 18 to 20cubic feet (according to the purity of the gas)are required to give a light equal in durationand in illuminating powers to lib. of tallowcandles, six to the pound, provided they were-set up and burnt out one after another.*

FURTHER ILLUSTRATIONS

OF THE

'MODE OF COMPUTING THE RELATIVE COST OR VALUE

OF

LIGHT,

EMITTED BY MEANS OF

CANDLES, LAMPS, & OTHER BODIES.

It is sufficiently known that the light of acandle, which is so exceedingly brilliant whenfirst snuffed, is very speedily diminished to

* 112 lbs. of Newcastle coal, called Tanfield Moor, pro-duce, upon an average, from 250 to 300 cubic feet of gas,fit for illumination.