PREFACE.

11 , Compton Street Soho.

THE following pages are intended to exhibit asummary view of the new art of procuring light, bymeans of carbu retted hydrogen gas obtained frompit-coal, and which of late has been employed withunparalelled success, as a substitute for candles andlamps, and is known by the name of Gas-Light .

To accomplish this object, I have given, in thefirst part of this Essay, a concise and popular viewof the chemical theory and production of artificiallight—-I have explained the action of candles andlamps—I have shown the methods of measuringthe comparative illuminating power of artificiallight of different kinds, so as to appreciate theireconomical value—-I have stated the proportionsof combustible materials requisite for producing alight of a certain strength ; with such other preli-minary facts and observations as were deemed neces-sary to enable the reader to understand fully thenature of the new art of illumination, which it is theobject of this Essay to describe.

These positions are followed by a chemical viewof the general nature and composition of coal—thechemical changes which this substance suffers, whenemployed in the production of gas-light—the dif-