In all processes of the arts where a moderate heat is wanted the gas-light flame will be found very advantageous--even on a large scale this flame may be used with profit. It possesses advantages which cannot be obtained from flaming fuel, where much nicety is required; because no fuel can be managed like the flame of coal-gas. For it is well known, that when too little air be given to flaming fuel it produces no flame, but sooty vapour; and if too much air be admitted to make those vapours break out into flame, the heat is often too violent. It is a fact, that flame, when produced in great quantity, and made to burn violently, by mixing with a proper portion of fresh air, driving it on the subject, and throwing it into whirls and eddies, thereby mixing the air with every part of the hot vapour, produces a very intense heat. The great power of a gas-flame does not appear when we try small quantities of it, and allow it to burn quietly, because the air is not intimately brought into contact with it, but acts only on the outside; and the quantity of burning matter in the surface of a small flame is too minute to produce much effect. [Illustration] But when the flame is produced in large quantity and is freely brought forward into contact and agitated with air, its power to heat bodies is immensely increased. It is therefore peculiarly proper for heating large quantities of matter to a violent degree, especially if the contact of solid fuel with such matter is inconvenient. As the gas-flame may be made to assume any shape and intensity, and as there is nothing to spill, it may be exhibited under such variety of forms and designs, as cannot fail to give rise to the most tasteful ornamental illumination. PLATES III. IV. and V. exhibit such designs of different kinds of gas-lamps, chandeliers, lustres, candelabras, &c. as are already in use in this Metropolis. PLATE III. fig. 1, represents a _Rod Lamp_. The gas passes through the rod _a_, to the Argand burner, which is surrounded by a cylindrical chimney, _c_, swelling out at the lower extremity. The construction of the Argand burner we have mentioned already, _p._ 78. In all the gas-light burners, constructed on Argand’s plan, care should be taken that the flame be in contact with the air on all sides, and that the current of air be directed towards the upper extremity of the flame. This may be effected by causing a current of air to rise up perpendicular from the bottom of the chimney glass, and to pass out again through the contracted part, or upper extremity of the chimney; but no other current of air should ever be permitted to come near the gas-flame, or enter the glass chimney which covers or defends the light; for if more air be permitted to mix with the flame than is sufficient for the compleat combustion of the coal-gas, it necessarily diminishes the heat, and consequently reduces the quantity of light.