190 Secent Improvements in Cider and Perry Ilakinig. 
and iaserted in the cask into wliicli the liquor is to be racked, and allowed 
to burn untU it goes out. The cask is then full of sulphurous fumes, and 
while in this state the liquor is run in. This absorbs the sulphurous acid 
gas, which kills the yeast-plant without retaining anj taste or smell. 
If fermentation should again set in, the operation must, of 
course, be repeated. The use of chemicals, however, and the 
endeavour to make good liquor from bad juice is the rock upon 
which cider has split and got its bad name. The best cider- 
makers never use them, and it may be laid down as an axiom 
that cider or perry is pure and good in the inverse ratio to the 
amount of chemicals used in its manufacture. 
Acetous Fermentation. — It is well known that all weak fer- 
mented liquors, when exposed to the action of the air for any 
length of time, become sour and turn to vinegar. As has been 
above stated, this will be spoken of as a chemical reaction, 
although M. Pasteur asserts that it cannot take place without 
the presence of a small microscopic fungus, called Mycodermes 
aceti. The chemical action, whether due to the presence of the 
fungus or not, is as follows : the alcohol in the liquor absorbs 
oxygen from the air and forms aldehyde and water; but the 
aldehyde in ordinary acetous fermentation never appears, the 
aldehyde taking up oxygen from the air at once and forming 
acetic acid. The fungus is visible to the naked eye, when in 
large quantities, as a blue mould on the top of the liquid, 
which at length sinks, and is then well known as tlae vinegar 
plant. 
Viscous Fermentation, or Iioiyincsss. — This peculiar change 
which sometimes accompanies \'inous fermentation manifests 
itself by the liquor becoming thick and viscous to such a 
degree that Avhen poured from one vessel to another the liquor 
draws into long threads. According to Pasteur, this is due to 
the presence of a very minute fungus with spherical cells, which 
has not as yet been named, but which has the property of 
changing the glucose into a kind of gum, which is always 
accompanied by mannite and the evolution of carbonic acid gas. 
In some seasons this fermentation is very troublesome, and un- 
fortunately the remedies recommended to cure it are as bad as 
the disease. 
Putrid Fermentation. — This is not a fermentation at all, but 
is due to the presence of bacteria and vibriones, whose position 
in the world of life has not yet been determined. Suffice it to 
say that their genns are always jiresent in the air, ready to 
seize any opportunity which may present itself favourable to their 
growth, and that, although there is no cure for this kind of fer- 
mentation, it may be prevented almost entirely by scrujiulous 
cleanliness in all the operations of making. 
