1 represents the gasometer; 4, the gas generator; 11, the funnel through which the water is introduced into the generator through the pipe, 13; 12, the pipe that connects the generator with the gasometer; 5, a stopcock with counterpoise that alternately opens and closes the communication between the funnel and the generator; 10, a lever connected with the cock, 5; 2, a chain that moves with the holder and maneuvers the lever, 10. The plug, 6, of the cock, 5, is provided with two conduits, 7 and 8, at right angles. This plug turns 90 degrees, when it is maneuvered by the chain of the gasometer. In the position shown in Fig. 13 the holder is at the top of its travel, and the counterpoise, 9, of the cock is in the position marked by dotted lines in Fig. 9. [Illustration: FIGS. 11, 12, AND 13.--DETAILS OF THE DICKERSON ACETYLENE APPARATUS] In this case, a charge of water fills the chamber 7 and 8 of the cock. This chamber may be oblong, as shown in Fig. 12, in order to increase its capacity. On the contrary, in the position of the counterpoise, 9, marked in continuous lines in Figs. 9 and 11, the channel, 8, communicates with the pipe, 13; the charge of water of chamber, 7 and 8, has fallen upon the carbides, but another quantity of water has not been able to enter, because the revolution of the cock has cut off all communication between the funnel, 11, and the generator, 4. The acetylene produced by the reaction of the water upon the carbide raises the gasometer holder, which then actuates the plug, 6, of the cock, 5, and allows a new charge of water to enter the chambers, 7, 8. It is only when the holder descends anew to the position, 1, that the water in the chamber, 7, 8, can fall upon the carbide. The quantity of water that the cock is capable of containing is not sufficient to produce a quantity of gas exceeding the capacity of the gasometer, and, as it is impossible to introduce another quantity of water as long as the gasometer has not been emptied anew, any overproduction of gas is thus rendered impossible. Fig. 10 applies to the introduction of the carbide into the water. It is necessary in this case that the carbide shall have been previously reduced to powder. The funnel, 11, is then closed by a cover, 21, in order to prevent any accidental escape of the gas. The carbide falls into the generator, the bottom of which is open. The latter enters a tank into which flows a current of water, escaping through the waste pipe, 19, in carrying along the lime formed. The height of the water in the tank is sufficient to furnish the pressure necessary to allow the gas to enter the gasometer through the pipe, 12. * * * * * DEVICE FOR THE DISPLAY OF LANTERN SLIDES.