The scheme of lighting houses, streets, and manufactories, by means of the inflammable gas, obtainable by distillation from common pit-coal, professes to increase the wealth of the nation, by adding to the number of its internal resources, and on this ground it is entitled, at least, to a candid examination. The apparent slight that has been thrown upon this new breach of civil economy by some individuals, who appear to be incapable of judging of its nature, has contributed to deter sensible and well disposed persons from wishing it success. It is the more necessary to state this fact, because, when a mistaken notion once becomes diffused, concerning the nature of a new project, persons of the best intention are liable to become affected with wrong impressions on their mind. I am neither a share holder, nor a governor, nor am I directly or indirectly concerned in any gas-light association. The object of the succeeding pages, simply is to rescue the art of illumination with coal-gas from misconception and misrepresentation, and by a fair, and not overcharged statement of its merits and its disadvantages, to appeal from prejudice and ignorance, to the good sense of the community. PART I. PRODUCTION OF ARTIFICIAL LIGHT; AND THEORY OF THE ACTION OF CANDLES AND LAMPS. The flame of burning bodies consists of such inflammable matter in the act of combustion as is capable of existing in a gazeous state. When all circumstances are favorable to the complete combustion of the products, the flame is perfect; if this is not the case, part of the combustible body, capable of being converted into the gazeous state, passes through the luminous flame unburnt, and exhibits the appearance of smoke. Soot therefore always indicates an imperfect combustion. Hence flame is produced from those inflammable substances only, which are either totally volatile when heat is applied to them, so as not to alter their chemical habitudes--or which contain a quantity of combustible matter that is readily volatilized into vapour by heat, or the elements necessary for producing such vapour or gazeous products, when the chemical constitution of the body is altered by an increase of temperature. And hence the flame of bodies is nothing else than the inflammable product, either in a vaporous or in a permanently elastic gazeous state. Thus originates the flame of wood and coal, when they are burned in their crude state. They contain the elements of a quantity of inflammable matter, which is capable of assuming the gazeous state by the application of heat, and subsequent new chemical arrangements of their constituent parts.