Sept. 19, 1872] 



NATURE 



419 



that liquids the most variable, even common household 

 broth, preserve their limpidity for years by being kept 

 from contact with air, provided that they be deprived of 



their germs. In the ordinary processes for manufactur- 

 ing beer, all these germs are carefully accumulated in the 

 wort, and even in the b;er ; an i basidc=;, the aromatic part 



oi the hops is utterly destroyed by the oxygen of large 

 masses of air ; hence a deterioration of the product and a 

 difficulty in keeping it. 



" The cooling of the wort can be^histened by various 

 arrangements. One of the most simple consists in having 

 serpentine or cylindrical tubes placed vertically in the 



