g' is the lever regulating the amount of air admitted to the twin tap, and by means of which the quality of the mixture is controlled. It is generally called the 'quality lever,' as it determines the quality of the mixture.

g is the lever regulating the aperture in the bottom of the twin tap, by means of which the perfect mixture is admitted to

the combustion chamber of the engine through the pipe e—in other words, it is a throttle lever. It is generally known as the 'quantity lever,' as it regulates the quantity of mixture reaching the combustion chamber, and consequently the force of the explosion.