and the Method of making Wines . 355 
in a state of fermentation, and to burst at the surface ; 
their passage through the strata of the liquid agitates all 
its principles, displaces all their moleculse, and there soon 
results a hissing noise similar to that produced by a gen- 
tle ebullition. 
Small drops, which immediately fall back, are then 
seen to rise several inches above the surface of the li- 
quid. In that state the liquor is turbid, and every thing 
is mixed, confounded, agitated, &c* ; filaments, pellicles, 
flakes, grapes, and stones, float separately, and are push- 
ed, expelled, precipitated, and thrown up, till they at 
length settle at the surface, or are deposited at the bot- 
tom of the vessel. In this manner, and by a series of in- 
testine movement, there is formed at the surface of the 
liquor a crust of greater or less thickness, called by the 
French le chapeau de la vendange « 
This rapid movement and continual disengagement of 
these aeriform bubbles considerably increase the volume 
of the mass. The liquor rises in the vat above its primi- 
tive level. The bubbles, which experience some resist- 
ance to their volatilisation by the thickness and tenacity 
of the chapeau , force a passage to themselves in certain 
points, and produce abundant froth. 
The heat increasing in proportion to the energy of the 
fermentation, an odour of spirit of wine is disengaged, 
and diffused every where around the vat ; the liquor as- 
sumes a darker colour; and after several days, and 
sometimes even after a few hours, tumultuous fermenta- 
tion, the symptoms decrease ; the mass resumes its for- 
mer volume, the liquor becomes bright, and the fermenta- 
tion is almost terminated. 
Among the most striking phenomena and the most sen- 
sible effects of fermentation, there are four principal ones 
which require particular attention ; the production of 
