83 



arrows, and hence will be washed clear of oferms. On the increase of 

 pressure through fermentation activit}' the o-as passes out at low pres- 

 sure by depressing- the li(|uoi- in (/>) until it gains exit, as indicated by 

 the arrows. This is the Xocl air controller; but in the writer's work it 

 has proved entireh^ too complicated and too ditlicult to keep clean for 

 practical use. The principle of air control is undoubtedly correct, 

 but it is better accomplished b}' some of the following- devices: 



The German ••fermentation funnel" (tig. 16) is a sini])lc and far 

 better device for controlling the air. This is a pottery or porcelain 

 device having- a central tapering- stem (a) with a l)asin-like vessel (^ 



Fig. 16.— German earthenware ventilating funnel— vertical section. 



around its upper end. The central stem (r) rises nearly to the height 

 of the outer rim, and is hollow. Over this hollow stem rests a remova- 

 ble cap ((/). which extends to the bottom of the basin. The lower rim 

 of this cap where it rests under the liquid is notched for the pas.sage 

 of gases, as indicated by the arrows. This device is inserted in the 

 bung-hole of the cask, and by reason of the tapering- stem can be made 

 to tit quite tightly: but it is always better to use some parathn wax 

 around it. The control liquid is placed in the outer basin until it is 

 about one-third full: then the cap is put on and the device is ready for 

 operation. While this is an awkward looking- device, it is the best 



