This reservoir, shown at ‹I›, Plate 25, is also a light, hollow sphere 120 mm. in diameter; both this and the air chamber being made by soldering hemispheres [p113] of copper together at their circumferences. There are three openings in the reservoir tank; two at the top and one at the bottom. One of those at the top serves for the admission of the 5-mm. pipe bringing compressed air from the air chamber; the other is connected with a pipe 1 cm. in diameter, through which gasoline is supplied to the tank, and which is closed by a simple plug at the top. The hole in the bottom serves as the outlet for the gasoline to the burners. Close to the bottom of the tank there is placed a small needle valve, which serves to regulate the flow of oil, for, were the pipe left open, the compressed air would force the oil out with such rapidity that the burners would be flooded and the intensity of the flame impaired. The construction of this valve is clearly shown in Plate 26A. It consists of a brass shell having one end (‹a›) soldered to the bottom of the tank. The needle enters through a stuffing box whose gland is held by two small screws. The stem of the needle is threaded and engages in a thread cut in the body of the casting and is operated by a fine wire on the outside. It will readily be seen that this device affords a means of making a very accurate adjustment of the flow of the liquid to the burners. After leaving the needle valve the gasoline flows along the pipe ‹S›, Plate 25, until it reaches the evaporating coil, ‹N›. In order to subject the oil to as large a heating surface as possible, in comparison with the sectional area through which it is flowing, the pipe, which left the needle valve with a diameter of 6 mm. soon contracted to 5 mm., is here flattened to a width of 7 mm. and a thickness of 2 mm. There are seven complete turns of this flattened tubing coiled to an outside diameter of 30 mm. At the end of the seventh coil the pipe is enlarged to a diameter of 1 cm. and two coils of this size are added, the inside diameter being the same as that of the flattened coil. This enlarged portion serves as a sort of expansion chamber for the complete gasification of the gasoline, which is then led back through a turn of the enlarged pipe, beneath the coils and to the front. At the front end of the coil a small branch is led off, forming a “bleeder,” which takes sufficient gas to supply the burner by which the coil is heated, the products of whose combustion pass into and between the coils of the boiler like those of the regular heating burners. The gas pipe rises in front of the coil and by a ‹T› connection branches to the two burners that are placed in front of the coils of the boiler. These burner pipes are 5 mm. in diameter and enter sheet-iron hoods forming regular burners of the Bunsen type, which are fully shown in all their details in the accompanying engraving, Plate 26. The pipe is plugged at the end, and a hole 0.9 mm.