When the art was yet in its infancy, I published a Treatise, containing a description of the apparatus and machinery best calculated for illuminating streets, houses, and public buildings, by means of coal gas, with remarks on the utility, safety, and general nature of this new branch of domestic economy, as far as then understood, and practised in the metropolis. The universal avidity for information on the subject, more perhaps than any particular merit in the work itself, produced a demand in this country for four large impressions of this work, in the course of a few years, and I have also had the satisfaction of finding that the Treatise has been translated into the French, German, and Italian languages. Since this work was written, however, the art of manufacturing and applying coal gas, has undergone so many material improvements, all combining to bring it to a degree of simplicity, precision, and economy, far surpassing every thing which the original mode of practice exhibited, that I have felt I should be guilty of an injustice to the constant demand which still exists for my former Treatise, had I not made it my duty to publish the work I now present to the reader; superseding altogether the former publication, but superseding it from circumstances of necessity, and with a view to good, which I trust will be found not illusory. The present treatise, as its title expresses, is intended to exhibit the superior process of manufacturing coal gas now employed in the metropolis and the provincial towns of Great Britain, and to lay before the reader the elevations, sections, and plans of the improved Gas Light machinery, which has stood the test of practice, and is now in action at the most celebrated Gas Light Establishments. In the first and second part of the Treatise, I have, as introductory to the rest, given a sketch of the chemical theory and production of Gas Light. I have pointed out the leading objects of public and private utility, to which the art of lighting with gas has been, or remains to be applied: and added such other facts and observations as may serve to remove all doubt in the minds of the reader as to the important benefit which this country in particular, and the world at large, have gained by this discovery. In the third part I have stated the maximum quantities of gas obtainable in the large way, from different kinds of coal. In the fourth part, I have given a description of all the various forms and dimensions which the distillatory vessels or retorts have successively assumed, as well as of the improvements that have been made in the mode of setting the retorts, with a view to saving them from undue deterioration, and preventing any improvident waste of fuel. I have here given a particular account of the distillatory apparatus now used at the most celebrated gas works in the metropolis.