Fig. 2. _A Rod Gas Lamp, with branches._ The gas passes through the hollow rod, _a_, and part of the hollow branch, _b_, to the burner of the lamp. The cylindrical shaped glass, _c_, exhibited in this figure, is not so well adapted for the compleat combustion of coal-gas, as the belly-shaped chimney, _c_, represented in fig. 1, 3, 5, 6, because the ascending current of fresh air is not turned out of its perpendicular course, and thrown immediately in a concentrated state, into the upper part of the flame where the combustion of the gas is less perfect. The exterior current of air which enters at the bottom into the lamp, rises merely with a velocity proportioned to the length of the cylinder, and to the rarefaction of the air in the same, but without being propelled to the apex of the flame, as it should do, and is made to do, in the bellied glass adapted to the lamp, fig. 1. Fig. 3. _A Bracket Lamp._ _a_, the tube which conveys the gas to the burner; _b_, the stop-cock of the tube. Fig. 4. _A Pendent Rod Lamp_; in which the gas is supposed to come from a pipe above, through the ceiling, into the pipe, _a_, to supply the burners. The tulip-shaped chimney, _b_, of this lamp, is likewise ill adapted for gas-light burners. Fig. 5. _A pendent double-bracket Lamp._ The gas passing through the perpendicular tube, _a_, into the brackets, _b_ _b_; _c_ shows the Argand burner. Fig. 6. _A swing Bracket Lamp._ _a_, the gas-pipe with its stop-cock; _b_, a brass ball, communicating with the pipe, _a_; _c_, the conducting tube, ground air-tight into the ball, _b_, and communicating with the burner of the lamp, so as to allow it to have an horizontal motion. Fig. 7. Shews the construction of the ball _b_, and pipe, _c_, of the lamp, fig. 6. Fig. 8. _A Swing Cockspur Lamp_, constructed upon the same plan as fig. 6. These two lamps are very convenient for desks in counting-houses, &c. Fig. 9. A stop-cock with ball and socket, which, when adapted to a gas-light pipe, allows it to have an universal motion, so that the light may be turned in any direction. Fig. 10. Section of the stop-cock, with ball and socket. Fig. 11. Shows the ball and socket, fig. 9, in perspective. [Illustration] PLATE IV,[26] fig. 1. _A Candelabrum_; the gas pipe ascending from the floor of the apartment, through the column _a_, and terminating in the burner of the lamp. [26] The gas-lamps exhibited in this plate, are employed in the library, counting-house, warehouse, and offices of Mr. ACKERMAN, and, by whose permission, they are copied on this occasion. Fig. 2. _A fancy pendent Cockspur Lamp._ The gas being transmitted to the burners, _c_ _c_, by means of the pipe, _a_. Fig. 3. _A Pedestal Argand Lamp._ _a_, the pipe and stop-cock, which transmits to, and shuts off the gas from the burner of the lamp. Fig. 4. _A Pedestal Cockspur Lamp._ _a_, the stop-cock and gas-pipe.