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tions of crushing, pressing, and filtering it is the cause of the oil 
turning rancid and lacking in keeping quality. The picked olives 
having been cleaned on the winnower, and if necessary washed, as 
is the case when they are swept from the ground under the trees, 
they are crushed fresh; when sound and in good order they may 
be allowed to be spread on the floor for a few days in layers a few 
inches thick until they can be crushed; during that time they 
wither and lose a certain amount of their water of vegetation. 
The crushing is done over a grooved, circular cement trough 
by rotating, heavy millstones, which reduce flesh and stones into a 
mash. Instead of millstones, crushers like those used for grapes 
are used; they consist of a hopper over two cylinders of cast- 
iron, fluted, horizontal and turning slowly in opposite directions. 
The paste is collected into a tub and put into flat bags or 
envelopes made of specially woven esparto grass, of rushes, a 
coarse cotton fabric, or even hessian. In some parts of France it 
is customary to sprinkle over the paste, before putting into the 
bags, a small quantity of vinegar, or of a decoction of tannin- 
bearing bark to coagulate the mucilaginous matter and facilitate 
the flowing out of the oil. A dozen or more of these flat pulp bags 
are piled up on the platform of the press, light wooden battens or 
tinned dises being sandwiched in between to favour the running of 
the oil when the pressure is applied. 
Instead of the pulp bags, a galvanised iron cylinder, reinforced 
with iron hoops and perforated with holes, may be used; the 
flowing of the oil from the metal recipient is facilitated by insert- 
ing perforated boards or mats of rushes at short intervals through- 
out the paste; lining with sackcloth inside prevents the pulp being 
squeezed out. Pressure is brought on gradually, to allow the oil 
to flow out. The first run is the virgin oil. The pressings are col- 
lected in tinned receivers and transferred to larger ones when it 
settles, the lighter oil floating over the dregs is carefully skimmed 
off with a tin ladle or else with cotton or a sponge. There still re- 
mains some oil in the water of vegetation and the dregs; these are 
collected in bigger reservoirs where in time the oil separates and 
floats, when it is collected. 
When the first crushing is done the press is opened and the 
compressed mash is broken up; some pour a little boiling water 
over it to coagulate the albuminoid matters, others prefer, for that 
purpose, a solution of some mild vegetable acid—citrie, acetic, or 
tannic. Pressure is brought on again and a further quantity of 
oil is extracted from the squeezed-out liquor. 
The clarification of the oil is effected by natural means, i¢., by 
rest and decantation, or by artificial means, such as filtration and 
treatment with vegetable acids for fine oils or with mineral acids 
and alkalies for the common oils. After a few days’ rest the oil 
