Figure 6 gives a sectional view of the generator with the cartridge in place. _D F G H_ represent the valve frame and _I_ the cartridge attached. The reservoir _A_ is filled with water, and when the frame is immersed, with the valve _R_ closed, the air contained in the cartridge and tubing can not escape, the water seal preventing, while the confined air prevents the water from rising in the tube _N_. When the valve at _R_ is opened and the air is allowed to escape, part of the water from the reservoir rises into the tube _N_ and then out through the small hole _O_ to the carbide. Gas is immediately generated, the pressure of which prevents further ingress of the water from the tube _N_, and the generation of gas is suspended. As the gas passes out through the valve at _R_ the pressure decreases, permitting the water to again rise in the tube and flow through _O_. Gas is again generated, which at once exerts its pressure and cuts off the supply of water. This is the automatic action by which water is brought in contact with the calcium carbide. Thus it will be observed that the use or escape of the gas regulates the generation by the simple device of the rise and fall of a water column. There is a cap _M_ screwed over the tube _N_. This is used to deflect the course of the water downward, so that the carbide in the lower part of the cartridge is first attacked. There is a needle inside of cap _M_, which can be used for cleaning the hole _O_. When the gas is generated it passes through the filter _D_ on its way to the burner through _R_. This filter consists of a tube loosely packed with ordinary nonabsorbent cotton, which should never cover the escape pipe leading to the valve _R_. In passing through this cotton filter moisture and dust are removed from the gas. In the latest model a felt filter is used instead of cotton. [Illustration: FIG. 6.--Signal lantern generator.] The escape pipe _F_ provides a means for the escape of gas generated and not used or generated more rapidly than consumed. Should an excess be generated, it passes down through the tube _F_, and, finding its way through some small holes in the bottom of this tube, escapes through the water seal and the opening at _C_. It will be noted that if escaping gas at _C_ should become accidentally lighted, the flame can not strike back into the filter and cartridge because of the water seal. The principal things to observe in the operation of this generator are the following: (1) To see that the rubber plugs _fit tightly_ into the openings of the cartridge. (2) That the tube _N_, the cap _M_, and water hole _O_ are not stopped up. (3) That the cotton in the filter is changed frequently. (4) That the _stopcock R is closed before inserting the frame in the water_. If this latter instruction is not complied with, it can be readily seen that the water will have free access to the carbide and excessive generation will occur.