176 
EXPRESSION OF OIL. 
When sufficiently ground, they are put into bags and boiled, 
or rather stewed, a short time, in a vessel containing a small 
quantity of water ; and are then transferred to a press, where 
they yield the oil. This press is of very rude construction. It 
consists of the hollowed trunk of a tree open at one end, and 
having two square holes mortised in its sides, opposite each other. 
It is so supported that the open end is higher than the other. When 
the oil is to be expressed, one of the bags is put into the trunk, and 
pushed back to its depressed end. Semicircular pieces of wood are 
then introduced through the mortices on each side, and meeting, form 
a circle, which is equal to the circumference of the hollow. Several 
of these are successively introduced, and fill up the interval between 
the bag and the mortices, and some space beyond, as shown in the 
figure. They are then driven back with great force upon the seed, by 
the means of bars and wedges of wood forced in by an immense 
hammer in the form of a battering ram. The oil runs from the press 
through a small opening in its depressed end. 
