196 VEGETABLE SUBSTANCES. 



The olive and the cornel are the only trees from 

 which oil is expressed from the pulpy part of the 

 fruit and not from the seeds alone. The oil obtained 

 from the kernel of the olive is supposed to become 

 rancid sooner than that contained in the outer part, 

 and therefore, in producing the best oil, care is taken 

 that the stones are not cracked in the preliminary 

 process of bruising the fruit, nor are they subjected 

 to sufficient pressure to produce this effect at first 

 when the best oil comes over. The press used for 

 this purpose is of a very simple construction. The 

 fruit is bruised by the action of a mill-stone, it is 

 then transferred to the trough of a screw-press, and 

 after as much oil is obtained as can be extracted by 

 the degree of pressure given, hot water is poured on 

 what remains in the trough ; the whole is then sub- 

 jected to stronger pressure, and a coarser product is 

 procured. When all the oil is entirely expressed the 

 refuse is used as fuel. 



The best soap is made of olive oil mixed with 

 alkalis, but its preparation for this purpose is not so 

 carefully conducted as when it is intended to form 

 an ingredient in food. Spanish soap, known in 

 England as Castile soap, is made with olive oil, 

 which is also largely used for the same purpose at 

 Marseilles, the merchants of which place carry on a 

 large export trade in soap. The heavy duty charged 

 on importing olive oil into this country, viz. 8. 8s. 

 per ton, effectually prevents its application to soap- 

 making in England, and we are consequently re- 

 stricted to the use of an inferior article. The 

 species of tree which bears the greatest quantity 

 of fruit, and not that which yields oil of the best 

 quality, is cultivated for this object. The fruit when 

 gathered is laid up in heaps to produce a slight 

 degree of fermentation, by which means a greater 

 quantity of oil is obtained, but at the expense of 



