252 THE BOOK OF USEFUL PLANTS 



But for commercial oil production, mills are estab- 

 lished that handle the yield of entire sections, 

 tjius making the crop more profitable for all con- 

 cerned. 



The olives are dried slightly in the sun, or by 

 artificial heat, to make handling easier. Then 

 they are crushed, pits and flesh, to break the cells 

 that contain the oil. Next, the "pomace" is 

 formed into blocks a yard square and three inches 

 thick, called "cheeses," between folds of thick 

 linen crash. Ten cheeses, separated by frames 

 made of wooden slats, are piled one upon another, 

 and a gentle pressure starts the oil to flowing. 

 This is the best. It is called "virgin oil," and 

 generally goes in with the next grade, making the 

 most expensive quality sold. 



Before the third pressing, the cakes are broken 

 up in water, cold or hot. The last pressing gets 

 only inferior oil, used for lighting or soap-making. 



From the presses the oil flows into settling vats. 

 It is dark in color, and contains impurities that 

 form a sediment. From one vat to another the 

 oil is drawn, until, at the end of four or five 

 months, it is clear yellow, and ready for sealing 

 in bottles or tins. 



The Padres brought the olive trees from Spain 

 into Mexico, and California. The "Mission" 



