448 
65° I*. will rise in the vat, if the temperature be unchecked, to 80° 
or &)° F., whereas the same grapes vatted at a temperature of 
75° F, will rise to about 95° or 100° F. As that temperature is 
decidedly injurious to the yeast of wine fermentation (Saccharo- 
myccs ellipsoideus), and on the other hand is favourable to bacterial 
life, or the life of those microbes which are the cause of disease in 
wine, it is obvious that, where no artificial means are at hand to 
contiol the excess of temperature, the grapes should be vatted only 
when cool. 
Jt is therefore essential, whilst the grapes are fermenting, to 
ascertain, by means of frequent testings with the thermometer, what 
the temperature is inside the vat. 
The elliptic yeast does its best work between the temperatures 
of 75° and 90° F. Below 75° the S. pastorianus or the S. apiculatus, 
which, at best, are but very poor kinds of ferments, thrive best; 
above 95° the ferments of acetic acid and of lactic acid play an 
active part, the conversion of sugar into alcohol ceases through the 
death of the yeast of wine fermentation, and the vat gets “stuck,” 
with a proportion of unfermented grape sugar still left in it. Dur- 
ing the course of a sickly fermentation, not only does the work done 
by sickly yeast plants fall short, both as regards quality and quan- 
tity, compared with what healthy yeast plants would do, but the 
same circumstances which have brought about that unsatisfactory 
state of things, i.e., excess of heat, being favourable to bacterial 
life, it follows that the wine suffers in bouquet and aroma as well 
as in delicacy and purity. Besides, it becomes tainted by the dele- 
terious products of undesirable and injurious bacteria, turning fiery 
and | eady, and suffering greatly in character. 
These injurious bacteria, feeding on what sugar is left unfer- 
mented, and also on the spirit or on the tartar of the wine, cause 
lactic or mannitie, acetic, tartaric, and butyric fermentations, which 
form products giving sweet-sour or milk-sour acid and mousy tastes, 
all defects aggravated by keeping, causing the wine to become flat, 
turbil, and difficult to clear. 
. 
ReEvIvAL OF FERMENTATION. 
It some times happens that, in spite of all care and precaution, 
some vats get “stuck” before fermentation is completed. In such 
cases the remedy must be applied at once, and the wine-maker has 
the choice between several means of attaining that end. 
One of the simplest is to draw the wine from the hot vat and 
fill smaller casks or vessels in which it will soon cool, with the result 
that the ferments will revive and show a tendency to accomplish 
their work. When this is noticed, the wine is restored to the vat, 
and a small addition of must in full fermentation added at the same 
time will soon help to restore matters. 
