Copper ® 59 
rations, which are generally performed in cellars. They 
may be performed also on a ground floor if it be some- 
what damp, if the temperature be subject to little varia- 
tion, and if there be not too much light The first ope- 
ration is to make the husks ferment, which is called avim* 
For that purpose one of the vats is opened, and the husks 
are put into two others of equal size, taking care to ex- 
pose them as little as possible to the air, and not to com- 
press them. One vat full of husks ought to fill two, and 
to occupy a double space after this operation. In some 
manufactories the husks contained in a vat are distributed 
into twenty or twenty- five earthen vessels or jars called 
oules, and which are generally sixteen inches in height^ 
fourteen in diameter at the belly, and about twelve at the 
mouth. When the husks have been put into these ves- 
sels, they are covered by putting the lid merely on the 
opening without pressing it down. The covers are of 
straw, and made for that purpose. In this state the husks 
soon heat ; and this change may be known by thrusting 
the hand into them, and by the sour smell which they be- 
gin to exhale. The fermentation first takes place at the 
bottom of the vessel, and gradually ascending extends 
itself to the whole mass. It proceeds to 30 or 35 de- 
grees of Reaumur. 
At the end of three or four days the heat decreases, and 
at length ceases entirely ; and as the manufacturers ap- 
prehend the loss of a portion of the vinegar by the natu- 
ral effect of a heat too much prolonged, they take care af- 
ter three days fermentation to remove the husks from the 
fermenting vessels, in order that they may sooner cool. 
Those who employ vats remove them into jars, and 
those who use jars put them into others. Besides the 
loss of the acetous spirit, too great heat inclines the mass 
at the bottom of the vessel to become mouldy, which, 
renders it unfit for making verdigris. Some manufaetu- 
