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t is in many respects less admirable than the former.
Two other devices intended to give automatic working, which are scarcely capable of classification among their peers, may be diagrammatically shown in Fig. 3. The first of these (D) depends upon the movements of a flexible diaphragm. A vessel (_a_) of any convenient size and shape is divided into two portions by a thin sheet of metal, leather, caoutchouc, or the like. At its centre the diaphragm is attached by some air-tight joint to the rod c, which, held in position by suitable guides, is free to move longitudinally in sympathy with the diaphragm, and is connected at its lower extremity with a water-supply cock or a carbide-feed gear. The tube e opens at its base into the gas space of the generator, so that the pressure below the diaphragm in a is the same as that elsewhere in the apparatus, while the pressure in a above the diaphragm is that of the atmosphere. Being flexible and but slightly stretched, the diaphragm is normally depressed by the weight of c until it occupies the position _b_; but if the pressure in the generator (_i.e._, in _e_) rises, it lifts the diaphragm to somewhat about the position _b'_--the extent of movement being, as usual, exaggerated in the sketch. The movement of the diaphragm is accompanied by a movement of the rod c, which can be employed in any desirable way. In E the bell of a rising holder of the ordinary typo is provided with a horizontal striker which, when the bell descends, presses against the top of a bag g made of any flexible material, such as india-rubber, and previously filled with water. Liquid is thus ejected, and may be caused to act upon calcium carbide in some adjacent vessel. The sketch is given because such a method of obtaining an intermittent water-supply has at one time been seriously proposed; but it is clearly one which cannot be recommended.
[Illustration: FIG. 3.--TYPICAL METHODS OF AUTOMATIC GENERATION CONTROLLED BY A FLEXIB