SYSTEMATICALLY SELECTED YEASTS. 51 



be drawn into the cylinder, or the latter might collapse from 

 the external pressure of the atmosphere. Under the con- 

 ditions mentioned and at the ordinary temperature of the 

 fermenting cellar, the cooling takes about two hours. If the 

 cylinder is provided with windows these must not of course 

 be screwed down tight during the steaming, as they would 

 then crack ; they should be screwed down cautiously and 

 gradually when the operation is nearly finished. 



With regard to the small vessels of water d and o at the 

 bottom of the bent tubes, it may be stated once for all that 

 their only object is to indicate the direction of the air current, 

 whether outwards or inwards. 



The wort cylinder and its two pipes s u and k are sterilised 

 in the same manner, but the process of cooling is here 

 omitted. When the steaming is nearly finished, the cock of 

 the air-filter is opened and the wort is admitted. The wort 

 employed is the ordinary hopped lager beer wort, which has 

 been sterilised by boiling in the copper, and is run as hot as 

 possible through the pipe u (shown in Fig. 8 only) and the 

 pock s into the cylinder. Shortly before the steaming is 

 finished the pumping of the boiling wort on to the cooler is 

 commenced, and ten minutes later the cock s is opened. 

 The wort is allowed to run into the cylinder until it reaches 

 the upper cock q, and the cock s is then closed. It is advisable 

 to place a small bucket under the cock q to catch the wort 

 which runs out, and when this occurs the cylinder is known to 

 contain the desired volume of wort. The hot steam and air 

 escape partly through q and partly through the bent tube n. 

 It is advisable to run off the first small quantity of wort 

 which enters the cylinder by means of the cock r, as it is 

 mixed with water from condensed steam, which gives it a 

 disagreeable taste. When the desired quantity of wort is 

 in the cylinder the cocks q and s are closed. Air, sterilised by 

 passing through the filter, is now forced through the hot wort 

 for an hour before the cooling is commenced, and the aeration 



E 2 



