A HISTORY OF SCIENCE 



" Let us take a glass flask with a long neck of from 

 two hundred and fifty to three hundred cubic centi- 

 metres capacity, and place in it some wort, with or 

 without hops, and then in the flame of a lamp draw 

 out the neck of the flask to a fine point, afterwards 

 heating the liquid until the steam comes out of the end 

 of the neck. It can then be allowed to cool without 

 any other precautions ; but for additional safety there 

 can be introduced into the little point a small wad of 

 asbestos at the moment that the flame is withdrawn 

 from beneath the flask. Before thus placing the as- 

 bestos it also can be passed through the flame, as well 

 as after it has been put into the end of the tube. The 

 air which then first re-enters the flask will thus come 

 into contact with the heated glass and the heated 

 liquid, so as to destroy the vitality of any dust germs 

 that may exist in the air. The air itself will re-enter 

 very gradually, and slowly enough to enable any dust 

 to be taken up by the drop of water which the air 

 forces up the curvature of the tube. Ultimately the 

 tube will be dry, but the re-entering of the air will be so 

 slow that the particles of dust will fall upon the sides of 

 the tube. The experiments show that with this kind of 

 vessel, allowing free communication with the air, and 

 the dust not being allowed to enter, the dust will not 

 enter at all events for a period of ten or twelve years, 

 which has been the longest period devoted to these trials ; 

 and the liquid, if it were naturally limpid, will not be in 

 the least polluted neither on its surface nor in its mass, 

 although the outside of the flask may become thickly 

 coated with dust. This is a most irrefutable proof 

 of the impossibility of dust getting inside the flask. 



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