GASOGENES. 77 



A thinner piece of glass tubing, F, passes through this short 

 wide tube so as to reach down to the bottom of the lower 

 bulb; this glass tube is surmounted with a trigger valve and 

 jet exactly like that of a soda-water siphon, and is made to 

 screw air-tight into the top of the upper bulb. To charge the 

 machine this screw is undone, and the thin glass tube with valve 

 attached, F, lifted out. A long funnel, C, provided for the purpose 

 is inserted with the narrow end inside the porcelain wide tube, so 

 that by pouring drinking water through the funnel this lower 

 bulb is filled with water. The funnel is now removed, and a 

 shorter one, E, substituted, and the upper part of the porcelain 

 tube loosely covered with a conical piece of metal introduced 

 through the shallow funnel E, by a wire D. Some crystals of 

 tartaric acid and a proportionate quantity of " bicarbonate of soda " 

 are now poured in through the shallow funnel, the quantity 

 depending on the size of the gasogene ; the cone prevents these 

 substances from passing down through the porcelain tube into the 

 water, so they remain in the upper bulb, B (which must be 

 empty of fluid). The cone, D, is now removed, and the thin 

 glass tube and valve, F, introduced in position, and screwed up 

 tight. The gasogene is then turned on its side, so that some water 

 flows from A (which was at first the lower bulb) into the other, 

 13, through the porcelain tube. As soon as the water comes in 

 contact with the solid tartaric acid and bicarbonate of soda, it 

 begins to dissolve these substances, with the result of setting up 

 a chemical action that does not ensue as long as no water is 

 present; the gasogene being now placed erect, the effect of this 

 chemical change is to cause carbon dioxide gas to be evolved, which 

 gradually passes up the porcelain tube, and is ultimately dissolved 

 by the water. A considerable degree of pressure is thus generated, 

 the effect of which is that when the trigger valve is opened the 

 water in the lower bulb is forced up the narrow pipe, and escapes 

 at the jet just as the aerated water from a siphon, effervescing in 

 precisely the same way.* 



By placing a teaspoonful of fruit syrup, lemon juice in which 

 sugar has been dissolved, syrup of ginger, or such like flavouring 

 matter, in the tumbler in which the aerated water is received, 

 delicious summer drinks are obtainable, especially if a little 

 crushed clean ice is also added to cool the beverage. 



* The portable fire-extinguishing machine known as an " Extincteur " 

 acts on precisely the same principle; by striking a knob on the outside cer- 

 tain chemicals become mixed together with water inside in such a fashion as 

 to generate gas, and set up sufficient pressure to force out the effervescing 

 water in a stream through a flexible delivery tube attached on turning on 

 the tap connected therewith. 



