inlet R. This draught of air sucks a small quantity of gasolene from the opening of the needle valve and this, gathering upon the walls of the air passage, rapidly evaporates and is readily combined with the inrushing air and converted into an almost dry gas or vapor. The small amount of gasolene drawn from the full chamber is at once replaced by the automatic action of the float and float valve. The proportion of air to gasolene is easily and accurately regulated by means of the needle valve and air valve, D and O. It is usual to regulate the supply for the motor while running at medium speed and then by speeding up and slowing down so adjust the automatic air valve O, by means of the thumb nut W, that the best results are obtained at all speeds. The function of the check valve which is attached between carburetor and engine is merely to prevent the vapor in motor base from rushing back through the carburetor instead of upward through the by-pass to the firing chamber. It is therefore only necessary on two-port, two-cycle motors, for in the threeport type the piston itself acts as a check valve, while in four-cycle motors the mechanically, or spring, actuated intake valve prevents any backward pressure of the gases.

This carburetor, as well as those of other makes and most vaporizers, is also provided with a throttle valve K, operated by a lever P, and which shuts off all or a portion of the gas entering the chamber of the motor by closing the opening R. This lever may be so adjusted by the set-screw S that the throttle cannot be completely closed, but will serve to feed just the right

amount of vapor to operate the motor at the slowest possible speed.

Another excellent carburetor of the float-feed type is the "Krice" illustrated in Fig. 61. In this carburetor C is the motor connection, D the cylindrical throttle; E the annular gasolene openings; F the gasolene level

and float; G the gasolene bowl; K the needle-valve adjustment; L the throttle lever; M the air intake; R the inlet valve operated by the float; T the gasolene connection; U the needle valve; and V the drain cock. The advantages claimed for this carburetor are that the gasolene, instead of being drawn from the needle-valve opening direct, is drawn through a narrow slit or opening nearly three inches in circumference and 1/100 of an inch wide and is vaporized within the chamber H, thus

producing more rapid evaporation and drier gas. The throttle D is also novel, being semi-cylindrical in form, and not only acts as a throttle, but also as an air adjustment for varying speeds of the motor.

Still another excellent type of float-feed carburetor

is the "Kingston" illustrated in Fig. 62. This carburetor acts on the same general principle as those already described, but has five supplemental air-supply inlets which are automatically opened and closed by bronze balls M, which float within the retainers N at high speeds, but close against their seats at slow speed, thus doing away with the more uncertain spring action of other automatic air-regulating devices. As a rule

the simpler and more positive the better in carburetor design, for a slight derangement in any part will result in variation of mixture and loss of power or stoppage of the motor.

A form of mechanically operated mixer is shown in Fig. 63, which represents the mixer used on the Cadillac

Fig. 63.-Mechanical Mixing Valve (Cadillac)

single-cylinder automobiles. In this cut, A represents the inlet to the motor; B the gasolene inlet; C, the air intake; D, the needle valve; E, the diaphragm; F, the valve seat; G, the adjusting screw; H, the mixer binder; I, the needle-valve spring; J, the binder screw; and K, the adjusting-screw binder. In operation the air, drawn inward by the suction stroke of the cylinder, causes the diaphragm E with the needle valve attached

to lift from the valve seat and thus permit a small quantity of gasolene to escape and mix with the inrushing air. The screw G bears upon a spring H which presses upon the top of the needle-valve stem, and this spring and screw are adjustable by means of the binder H and screw J so that the spring exerts greater or less pressure upon the needle valve and thus allows it to raise higher or lower according to the requirements of more or less gasolene. When correctly adjusted this mixer gives excellent results, but the adjustments must vary with climatic variations and the conical head of the needle valve and its seat become rapidly worn and often permit too much gasolene to enter the chamber.

The carburetor of a motor is its most delicate piece of mechanism and has been aptly called the "Heart of the Gas Engine." It should never be tampered with until everything else has been looked over in case of trouble, for it is often the work of several hours to readjust a carburetor correctly. It is a very common fault of many operators to continually fool with the carburetor or even to use it to turn off the supply of gasolene by screwing the needle valve onto its seat. This is a practice that cannot be too strongly condemned. Turning the needle valve against its seat injures both valve and seat and it is practically impossible to adjust it once it becomes rough, burred, or bent. A regular cut-off valve or cock should be placed in the pipe line outside the carburetor, and this should always be used for shutting off the fuel supply when the motor is not in use. A great deal of trouble with carburetors is caused by water, or particles of dirt, getting in the gasolene and finding