Manufacture and Preservation of Cider an,d Perry. 85 
But of the cause of this change I believe very little is known. 
Professor Fownes, in his Manual of Chemistry, p. 417, says, 
"It is certain that decomposing' azotised bodies not only do 
possess very energetic and extraordinary powers of exciting 
fermentation, but that the kind of fermentation setup is in a great 
degree dependent on the phase or stage of decomposition of the 
ferment." He thus evidently thinks there are different kinds of 
fermentation resulting from the condition or character of the 
ferment. 
In a conversation I have recently had with Dr. Voelcker upon 
this subject, he told me that the principal point is to get a right 
kind of fermentation, as each kind of ferment produces a like 
fermentation in the liquor to which it is applied. Thus, if you 
apply the vinegar-plant (commonly called "mothers") you get a 
vinegar or acetous fermentation ; from a top yeast you get a top 
fermentation ; from a bottom yeast, a bottom fermentation ; from 
a ropy yeast, a ropv fermentation in the liquor to which it is 
applied. It has been said that each kind of ferment produces 
a separate and distinct plant of its own ; and this might pos- 
sibly account for the different kinds of fermentation in cider, 
which I will now proceed to explain, only premising that 
the temperature of the air and the condition of the atmosphere 
exert a powerful controlling influence on the character of the 
fermentation which is produced. 
We will first notice the vino*us fermentation. This has 
different stages. The first change we notice is that in which the 
liquid throws some of the sediment out at the bunghole, whilst 
another portion settles to the bottom, and this is often so com- 
pletely done that the liquor remains clear and blight. When 
violent fermentation afterwards sets in it makes the cider or 
perry thick and turbid, even if bright before ; and if this is 
allowed to go on it will spoil the cider in a few days. It is this 
second stage, or violent fermentation, which all cider-makers 
dread, and try to prevent, whilst the first they encourage as much 
as possible. This rapid or violent action is frequently mistaken 
for the acetous fermentation, because of the increased acidity 
ot the liquor, which, however, may generally be traced to an 
excess of malic rather than acetic acid. 
All cider-drinkers like the flavour of the malic acid ; but no 
one likes the acetic acid, or sharp taste. Malic acid is the 
natural acid of the fruit, and as long as the sugar or saccharine 
matter is in excess only the sugar is tasted ; but as the fermenta- 
tion proceeds the sugar is gradually changed into spirit, and then 
the malic acid gets in excess, and you taste its flavour. This 
accounts for the fact which has puzzled many persons, that a 
cask of cider may be found sweet one day, but acid when tasted 
