other useful functions: it serves to collect and retain all the liquid matter that may be condensed in the pipe _a_ from the spot at which it was originally level or was given a fall to the seal, as well as that condensing in _c_ as far as the spot where _c_ dips again; and it equally acts as a washer to the gas, especially if the orifice _g_ of the gas-inlet pipe is not left with a plain mouth as represented in the figure, but terminates in a large number of small holes, the pipe being then preferably prolonged horizontally, with minute holes in it so as to distribute the gas throughout the entire vessel. Such an apparatus requires very little attention. It may with advantage be provided with the automatic arrangement for setting the water-level shown at _d_ and _e_. _d_ is a tunnel tube extending almost to the bottom of the vessel, and _e_ is a curved run-off pipe of the form shown. The lower part of the upper curve in _e_ is above the level _f_, being higher than _f_ by a distance equal to that of the gas pressure in the pipes; and therefore when water is poured into the funnel it fills the vessel till the internal level reaches _f_, when the surplus overflows of itself. The operation thus not only adjusts the quantity of water present to the desired level so that _a_ cannot become unsealed, but it also renews the liquid when it has become foul and nearly saturated with dissolved and condensed impurities from the acetylene. It would be a desirable refinement to give the bottom of the vessel a slope to the mouth of _e_, or to some other spot where a large-bore draw-off cock could be fitted for the purpose of extracting any sludge of lime, &c., that may collect. By having such a water-seal, or one simpler in construction, between the generator and the holder, the former may be safely opened at any time for repairs, inspection, or the insertion of a fresh charge of carbide while the holder is full of gas, and the delivery of acetylene to the burners at a specified pressure will not be interrupted. If a cock worked by hand were employed for the separation of the holder from the generator, and the attendant were to forget to close it, part or all of the acetylene in the holder would escape from the generator when it was opened or disconnected.